Scratch your head on this one!

Started at Waterloo and finished at Upton Park. The clue was :"later this year"

Well, you could always do Oxford Circus (or Marble Arch) - Bond St. - Green Park - Finsbury Park, and this way you get 2 parks for the price of 1!!!!!!!

When whoosh mentioned later this year, I thought of Langdon Park the new station to open on the DLR....

bethnal green/bank - liverpool st - moorgate (circle/met) - upton park (h&c)

here's a cheeky one...
later this year can still be before queensway opens, so lancaster gate-nhg-bayswater-wimbledon park via the route given above.

west acton-ealing broadway-ealing common-hyde park corner (on a picc stopping at Turnham Green) is another cheeky one.

langdon park is between all saints and devons road and only Bow and Tower Gateway are viable interchanges to the DLR in terms of this quiz, and both are too close.

Where is that going to be?

just seen another 15
waterloo/st pauls/liverpool street - bank - moorgate - westbourne park/northwick park/moor park
bank / bethnal green - liverpool st - moorgate - westbourne park/northwick park/moor park

the moor park ones are fast, stopping at Wembley Park (which is the norm now anyway, and not some trick)

I was so interested in the trick I forgot that a normal Piccadilly would get you to Green Park! therefore, I make it 20 and have west acton - ealing broadway - ealing common - green park.

I think I'll leave it there: here's a list of viable interchanges (at the moment) onto the third line:
Ealing Common (start at West Acton)
High Street Ken (start at Lancaster Gate and Holland Park)
Bayswater (start at Lancaster Gate and Holland Park)
Baker Street (start at Marble Arch and Oxford Circus)
Green Park (start at Marble Arch, Bond Street, Oxford Circus and TCR)
Piccadilly Circus (start at Bond Street and TCR)
Warren Street (start at Bond Street, Oxford Circus, TCR and Holborn)
Leicester Square (start at Oxford Circus and Holborn)
Cannon Street (start at St Pauls and Liverpool Street)
Tower Hill (start at St Pauls and Liverpool Street)
Shadwell (start at St Pauls and Liverpool Street)
London Bridge (start at St Pauls and Liverpool Street)
Moorgate (start at St Pauls, Liverpool Street, Bank and Bethnal Green)
Aldgate (start at Bank and Bethnal Green)
Aldgate East (start at Bank and Bethnal Green)
Bow Road/Bow Church (start at Bethnal Green and Stratford)
Stepney Green (start at Bethnal Green and Stratford)
West Ham (start at Mile End and Leyton)

I've found some very annoying very close (eg 9/11 away, rather than 10) ones and some others, but i'll stick on 20 as I don't want to hog the quiz. BTW the "at the moment" is a big clue to another trick (also W&C is out in this list - can't give you all the answers)

EDIT:oops, had a station that shouldn't have been there as "at the moment" it's not a stop but it's been used anyway.

there's 45 routes that I have. we have 32 of them. there's 13 left (4 of which are 'trick').