Underground record breakers

Two British men are hoping to set a new record for visiting all of the UK's London Underground stations in one day.

Chris and Karl King from Sunderland are hoping to smash the existing record today by visiting all 270 stations on the rail network in under 16hrs 44min and 16 seconds.

The pair started at 6.22am this morning and will battle against packed rush hour trains, and hope they don't run into any unforseen delays which could hold up the attempt - such as signal failures - hoping to finish their task by around 11pm tonight.

Chris and Karl have undertaken transport challenges before - in 2008 they travelled to London and back only using local public transport, and in 2009 they visited 10 major cities in the same manner; however, they say this is their biggest task yet.

Chris, 35, said: "It's definitely a lot more of a challenge this time - it's the hustle and bustle of the London Underground that will make it difficult more than anything else."

The event takes place as part of Guinness World Records Day, which sees more than 300 record attempts take place around the world to commemorate the day in 2004 when the Guinness World Records annual became the world's best-selling copyright book.