On Saturday, I did the Alphabet Challenge (http://www.explorerticket.co.uk/tubechallenge/alphatop.htm). This involves starting at a station with a name starting with A, then going to one starting with B and so on. There are no stations starting with J, X, Y or Z. They must also be visited in order - if you pass through a C on your way from A to B, it doesn't count and you have to visit that C (or another) after the B.
Start at ALDGATE
Circle to Liverpool Street, dep. 10:01:34, arr. 10:02:55
Central, via BANK & CHANCERY LANE to Bond Street, dep. 10:06:49, arr. 10:18:00
Jubilee to DOLLIS HILL, dep. 10:20:28, arr. 10:36:04
Jubilee to Finchley Road, dep. 10:38:37, arr. 10:45:31
Metropolitan, via EUSTON SQUARE to FARRINGDON, dep. 10:46:21, arr. 11:02:37
Metropolitan, via GREAT PORTLAND STREET & HARROW-ON-THE-HILL to ICKENHAM, dep. 11:03:33, arr. 11:49:43
Metropolitan to KINGS CROSS ST. PANCRAS, dep. 11:52:04, arr. 12:35:27
Piccadilly to LEICESTER SQUARE, dep. 12:38:27, arr. 12:44:32
Northern to Tottenham Court Road, dep. 12:46:28, arr. 12:47:23
Central, via MARBLE ARCH to NOTTING HILL GATE, dep. 12:49:39, arr. 13:00:11
Central to OXFORD CIRCUS, dep. 13:04:27, arr. 13:12:42
Bakerloo, via PADDINGTON to QUEEN'S PARK, dep. 13:14:27, arr. 13:30:44
Bakerloo, via REGENT'S PARK to Oxford Circus, dep. 13:33:14, arr. 13:48:11
Central, via ST. PAUL'S to Bank, dep. 13:50:54, arr. 14:17:11
Transfer to Monument
District, via TOWER HILL to UPTON PARK, dep. 14:22:28, arr. 14:43:49
Special Circle to VICTORIA, dep. 14:45:40, arr. 15:18:43
District to WESTMINSTER, dep. 15:19:49, arr. 15:22:55
Elapsed time = 5:21:21
The big delay was being held behind a broken down train on the eastbound Central line. Oxford Circus to Bank took 26 minutes compared to the 9 minutes in the timetable.