Great Western Coffee Shop

Travelling from Egham to Colchester next week. Going on an early evening and want to divert in central london for a few hours before continuing on. With a straight through ticket from point to point, can i do this? E.g Egham to Waterloo, walk to venue, jump back on underground to Liverpool street later.

Best to get a one off underground ticket inbetween?

Cheers
John

Probably fine but you need to be slightly careful... Firstly it depends on the ticket type you're going to be using: nearly all "walk-up" fares (which would include anytime, off-peak or super off-peak tickets) allow you to break and resume your journey at an intermediate station. There are a few that don't though: if you can let us know what ticket type you'll be using the one of us can check the validity for you.

Note though that you cannot break your journey during the cross-London transfer on the Underground. You'd be fine to break your journey at Waterloo and walk to the venue, and would then have two options: if you walked back to Waterloo you could resume the journey using your National Rail ticket, which would be valid for the cross-London transfer to Liverpool St. Alternatively if that's a pain then just buy an Underground ticket from wherever you are to Liverpool St for a few extra pounds then resume your journey from there. Not having used the cross-London part of the journey shouldn't give you any problems.

As there are no Advance Purchase (break of journey forbidden) fares available for that journey I'm assuming you hold, or intend to purchase either an Anytime or Off Peak ticket.

These permit break of journey (BoJ) for the parts of the journey on National Rail, but if you wish to break your journey in London you will only be allowed to leave an intermediate (between Waterloo and Liverpool Street) London Underground station. You can't then re-enter the Underground system with the same ticket. Cross London transfers using the Underground with through National Rail (NR) tickets should be regarded as an additional benefit. A benefit that doesn't include the full BoJ permission allowed on National Rail.

Technically, it's more to do with the limitations of the National Rail tickets' mag-strip technology when read by Underground barriers, than denying flexible journey options to the passenger. It would be impossible to program all possible BoJ opportunities in Zone 1 between London Termini. What you've essentially got encoded on a National Rail ticket with a cross London transfer is one Underground entrance permission (at the arriving NR station - in this case Waterloo) and one exit permission (departing NR station). That exit permission will also allow you to jump off at an intermediate Underground station in Zone 1, but you won't then be able to rejoin later with the same ticket.
 
So, With the Egham to Colchester Anytime or Off Peak ticket you won't be able to break your journey at Waterloo and re-enter the Underground network elsewhere to get you to Liverpool Street. You can of course go back to Waterloo under your own steam and resume your journey from there.

In summary, you will need a single Underground ticket from where you plan to 'jump back on underground', if that is other than Waterloo, to get you to Liverpool Street. Bear in mind that'll cost ^4.30 for a Zone 1 single. Unless you have an Oyster Card, in which case the Zone 1 single on PAYG is ^2.00.

I disagree slightly on a matter of detail.  I don't believe the LU coding is clever enough to know that your arrival station is Waterloo, so you could enter the underground for the first time somewhere else, as long as it is one of the listed cross London interchange points.  In theory you are limited to entry and exit at interchange points that are appropriate to the overall route - but the ticket gates cannot know this.

So something like NR to Waterloo, then a walk to your venue, then enter LU at (say) Victoria and exit at Liverpool St would be possible.

The list of LU interchange points is long and varied:

http://www.nationalrail.co.uk/times_fares/ticket_types/crossing_london.html#travelling_connect

...so it may be that there is a much more suitable route combined with an initial walk - and of course from Egham your valid 'London Terminals' for arrival also include Victoria and Charing Cross (via Waterloo East) - the latter is not always realised.

PS, I'd better add that my usual use of this 'break potential' was to walk from Waterloo over Hungerford Bridge, and enter LU at Embankment.

Paul

AFAIK the ticket is encoded for one zone 1 LUL journey, as long as you enter once and exit once the ticket should be accepted.  And if it does get spat back out then I can't see gateline staff denying access.