please empty your brain below

London Bridge? It is the only station on both the Jubilee and Northern Lines. As well as being my station for work so I am keeping optimism alive.

Bank - it is on the central line, which connects to all other lines except the East London Line. From bank you can get to the ELL via the DLR.

Wait a sec - you can also get to the ELL directly from Bond St via the jubilee line! Hmmmm, what am I missing....

...maybe I was missing the non-Edgware road section of the district line. That takes 2 changes from Bond St.
My answer is Bank / Monument - they are really one station, aren't they?

Kings Cross?

Hmm.. Liverpool Street? Only one to be on H&C, Central and Circle. That pretty much covers all bases, can't think of any lines that dont intersect them..

probably wrong but... it is Kings Cross St Pancras? It's direcly on the northern (N), victoria (V), picadilly (P), circle (C), hammersmith and city (H), and metropolitan lines (M).

that leaves central (Ce), jubilee (J), district (D), Waerloo and city (W), East London (E) and DLR, plus 'national rail' on the map
Thus, one can change to stations on:
Ce at Liverpool Street (on C)
District Line Olympia loop at Edgeware Road)
The rest of D at Earl's Court
J,B, at Baker Street (via C)
DLR at bank (via N)
The woolwich to Richmond train at Highbury and islington (via V)
and E at Whitechapel (via H)...
now, what have i missed?

Earl's Court?

What is the catch in this question, anyone?

Given that Chesham needs a Change at Chalfont and Latimer (Metropolitan) and Mill Hill East needs a change at Finchley Central (Northern) then if there is a solution the station in question must lie on both those lines.

Mill Hill East doesn't require a change at Finchley Central, unless that's changed in the last couple of years, and Chesham can be reached by some trains from central London

Mill Hill East DOES require a change at Finchley Central in the middle of the day. Yes it has changed in the last couple of years.
There are NO direct trains to Chesham in the middle of the day.

As when doing exams read the question carefully.

That leaves Bank in the running I guess as it is on the Northern line. Is it cheating to count Bank and Monument as one station?

In fact, given that you have to change at Earl's Court to reach olympia, the station we need must be both on the District and Northern Lines therefore Bank or (I doubt it!) Embankment

Hmm, but how do we get from Bank to Chesham....????

Ah, Pedantic, I did read the question carefully; it was my knowledge that was lacking.

In that case, the argument goes like this: to get to Chesham, the station must be on the Metropolitan. To get to Mill Hill East the station must also be on the Northern. That leaves Kings Cross and Moorgate, both of which can also get to the ELL stations with one change. However, you can't get from Moorgate to Kensington Olympia without changing twice, which leaves Kings Cross as the answer.

Incidentally, if you change the time of day assumption, the answer changes so it really should be part of the question itself.

You don't need to change at Earls Court to go to Olympia. The service is normally a shuttle to High Street Kensington.

At the risk of further cluttering the tube map (see DG's post on Monday) I do wish they would make that clear on the map.

I was going to query whether DG meant the tube map as displayed or the real world because of the Olympia issue but in the end I convinced myself this was irrelevant.

In which case, I think Moorgate would also work, giving two stations as the answer.

I didn't know about the Mill Hill shuttle service, because it only started two weeks ago (link). It only operates between 10am and 4pm, and after 7pm... but that includes around noon.

So I have a nagging doubt that today's problem was solvable a fortnight ago, but might not be at noon today.

Dave, at first glance I think you right. I never thought of Moorgate and I just assume the question as stated was correct "There is only one station ..." Lets see DG get out of that one ! - or maybe I will end up eating humble pie later today.

Assuming having to change to reach Chesham...

Baker Street.
Reasoning: The station must be on the Met to reach Chesham. The Jubilee line is the only line that intersects will *all* other lines, making it a requirement for it to be a Jubilee station as well. The only other oddball station to get to is Olympia, and Baker St. is the only Met/Jubilee station on the Circle Line (change at HSK for Olympia).

Leaves out Mill Hill obviously, but we've discounted that for the purposes of making this possible.

The new Chesham timetable is another spanner in the works around lunchtime, because there are no longer any off-peak Aldgate-Amersham trains.

But if the time were 6pm rather than noon, then I think today's question has a number of solutions.

but Chz there is absolutely no requirement to intersect with LINES. The fact that the Jubilee line is the only line to intersect with all other lines is irrelevant.

Unless I have missed something then I would argue that if MHE is not included (sounds like a Mornington Crescent variation) then any station on both the Met (to change at Chalfont and Latimer for Chesham) and the Circle line (to change at HSK for Olympia) is good enough. The MHE issue only further restricts it to Kings Cross or Moorgate. From both these stations you can reach any other line (hence any other station) with just one change with the exception of the anomolies already
pointed out.

The challenge for me is to work out what DG thought the answer was and why.

I still think it's Kings Cross St Pancras.

Ealing Broadway anyone? Central and District intersect all other lines.

Or maybe I didn't understand the question

Is it Mile End? On the Central, District and Ham lines.

Shazzlebut! and Snap!

Er, Mile End? That makes sense to me.

They sneaked that change to Amersham off-peak trains in. Can't imagine they are too happy in Metroland. Still it doesn't alter the problem when based on the tube map - only in real life.

To summarise (I think):

• At noon today, the problem is impossible (thanks to the Chesham shuttle and the Mill Hill shuttle).

• At noon two weeks ago (before the Mill Hill shuttle was introduced) there was a unique answer.

• In the evening rush hour (when Chesham and Mill Hill both receive through services) there are multiple solutions. These include Kings Cross St Pancras, Mile End and Ealing Broadway, but also several other stations.

I disagree but we may be making different assumptions. it is incredibily difficult to formulate such questions unambiguously.

I think:

· At noon today there are two solutions possible (KX and Moorgate). If this is not true then someone please state a station that cannot be reached from these ones under the required conditions.

· At noon two weeks ago you could have had any combined circle/metropolitan line station

· In the evening rush hour any station that can reach any other line without a change of train would be a solution. You do not need to include the Waterloo and City as there are no intermediate stations to serve but you do need to treat the City and West End branches of the Northern line as separate entities. There are probably loads of these but they need to either be on the Jubilee, the District or the Hammersmith and City line as you need to be able the East London Line via Canada Water or Whitechapel.

Are we also assuming that the system is not in "Knip" and the Dollis Hill loop is removed?


Oops. I think my rush-hour solution ignored the Olympia issue. Any qualifying station has to be on the District, Hammersmith and City or Jubliee lines so you can reach the East London Line.

It also has to be on the District or Circle line so that you can reach the Olympia shuttle service.

Furthermore it is impossible to get from stations only on the Jubilee Line to Olympia with just one change of train.

The solution(s) therefore has/have to be on the [District or Circle] and [District or Hammersmith and City Lines. This means that it must either be on the District or both the Circle and Hammersmith and City Lines.
It also need a direct connection with a Metropolitan line station which cuts out a lot of District line stations but leaves some (i.e. Ealing Broadway, Westminster, Embankment, Mile End and all those that also serve the Piccadilly line.

At noon two weeks ago you couldn't have reached Chesham from Kings Cross or Moorgate.

So it must be Baker Street then, as it does have direct trains to Amersham requiring only one change at Chalfont & Latimer.

As I said it is extremely difficult to set these type of questions unabiguously. I was going by the link provided in the first line of your challenge and according to that Kings Cross to Chesham with just one change is possible.

I now realise the answer you were expecting was Baker Street.

What?! You mean it's OK to use a map to work this out?! Bugger, that's 2 hours of my life I'll never get back...

Yes, the 'noon' (2 weeks ago) answer was Baker Street. Phew, and hurrah!

I daren't ask for the 'evening rush hour' solution…

why are you all assuming that the journey has to be completed as soon as possible? you could START at noon .. change, and where you change onto the Met line, wait several hours until the evening rush hour until the first through Chesham train comes along.

In that case why assume it has to be made ONLY by train. Go to Amersham and catch a bus to Chesham! You have done it with only one change of train

The evening rush hour solution is:

i) any station Baker Street to Barking inclusive

ii) any District line station that is also a Piccadilly station as well

iii) any District line station that is a Circle line station as well

iv) Ealing Broadway

Get a taxi

I wonder how much employers' time this puzzle used up today, eh?

Pedantic - I agree whole-heartedly with your rush hour solution...
...except that in iii) you can't include the handful of District/Circle line stations between Paddington and High Street Kensington because no District trains run from there to Whitechapel.

At least I think I agree until somebody tells me that I'm wrong.

If we value work at the minimum wage, which is about £6 an hour, then I think conservatively we're talking 20 hours collective, so £120 cost.

Ah well, probably not really. Though this is how the CBI often works out things 'cost of traffic jams etc'.

Yep, DG, you are correct. I never intended the ones you mentioned to be included but even I failed to be pedantic enough to word it so they were not.

I should have said any District Line station with a direct service to Whitechapel that is also a circle line station or simply said except ...

So, is the answer Baker Street then? I've been monitoring this on and off between meetings at the office but didn't get a chance to offer anything. But if I had I would have said that I read somewhere that the Joob is the only line that connects with every other - which means that it had to be a Jubilee Line station. I have to admit I am still confused by the "time of day" and "two weeks ago" spanners, but if the Met Line complication is credible (ignoring the Northern Line one) then I would have said Baker Street or Finchley Road, as every Met Line train stops at both of these. Hurrah for the Jubilee! ??

Baker Street. Light in my head and dead on my feet. I know, DG, you've already done it. It's right though isn't it?

You want another summary? OK.

• At the start of this month, the correct answer to this problem was Baker Street. This was the only station from which you could get to Chesham (change at Chalfont & Latimer) AND Kensington Olympia (change at High Street Kensington) AND Wapping (change at Canada Water or Whitechapel) AND Mill Hill East (change at Kings Cross, St Pancras or Moorgate).

• On 15th October, TfL withdrew through trains to Mill Hill East during the middle of the day. A shuttle service now runs from Finchley Central to Mill Hill East between the morning and evening rush hours. And you can't get from Baker Street to Finchley Central, so the problem is now impossible to solve.

• But things are different during the rush hour. Before 10am and after 4pm there are through trains to Mill Hill East AND through trains to Chesham. So (deep breath), the rush hour answer is
i) any station from Baker Street to Barking inclusive
ii) any District line station that is also a Piccadilly station
iii) any District line station that is also a Circle line station (apart from those between Paddington and High Street Kensington inclusive)
iv) Ealing Broadway

Thanks for asking

What DG meant to say in iii) was apart from those between Edgware Road and High Street Kensington inclusive.

And before the 1st October when the revised Metropolitan Line timetable was introduced and no Amersham trains went beyond Baker Street there were quite a few off-peak solutions - any station on all of the Metropolitan, Circle and Hammersmith and City lines i.e. Baker Street to Liverpool Street inclusive

Erm, surely Edgware Road's allowed? (because you can take the Hammersmith and City line to Whitechapel to reach the East London line)

CORRECTION - as they say on the UndergrounD. DG was right in his latest post. Although you cannot go from Edgware Road to Whitechapel directly via the District line I forgot that you can do so using the Hammersmith and City line. This really ought to be logically included in
i) any station from Edgware Road to Barking inclusive

I am getting too old for this.

So, that's...
i) any station on the Hammersmith & City line from Edgware Road to Barking inclusive
ii) any District line station that is also a Piccadilly station
iii) any District line station that is also a Circle line station (apart from those between Paddington and High Street Kensington inclusive)
iv) Ealing Broadway

Can we stop now?

No-one has mentioned Green Park...

Mornington Crescent!

Well someone had to put a stop to this game......and I win!

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