If anyone wasn't taking Sol Campbell's bid for London Mayor seriously, they should be now: the former footballer has come up with a daring idea to help improve the tube.

Mr Campbell, who spent most of his professional career at Tottenham and Arsenal and won 73 caps for England, is hoping to be the Conservative candidate for the Mayor of London in 2016. His main opponent in the race is Zac Goldsmith, the Tory MP for Richmond Park, who officially announced his decision to run for City Hall after holding a consultation with his constituents on whether he should enter the race.

Mr Campbell appeared on LBC radio on Wednesday for a chat with presenter Beverley Turner and political editor Theo Usherwood. The politically inexperience Mr Campbell was asked by Mr Usherwood about his plan for the capital's transport network.

"With the Tube, it just needs more investment," Mr Campbell replied, in a rather generic phrase. However, he then made a rather novel suggestion, arguing that the platforms across the Underground could be lengthened, as if such a feat would be simple to do on a 150-year-old network and across all 270 stations.

"Maybe lengthening some of the platforms to get more carriages in, things like that. It just needs more investment put into it."

Mr Usherwood, clearly somewhat bemused by Mr Campbell's argument, asked the former England defender whether he regularly used the Underground.

"I’m not a regular user but I have used it," Mr Campbell replied, revealing that he last used the trains two or three weeks ago. However, Mr Campbell does not own an Oyster card because he uses his credit card. "I like walking as well," Mr Campbell chimed.

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There was more awkwardness to come when Mr Usherwood - clearly realising that the Tube was nor Mr Campbell's forte - asked what route the Conservative hopeful would take if he was travelling from the Emirates, the home of his former club, to City Hall.

"The best one would be London Bridge or Tower Hill...You’d go probably along Holloway Road...Piccadilly or Northern?"

Tfl says the best route would be the Piccadilly line from Arsenal to King's Cross, the Northern line to Bank, a short walk to Monument, and finally the Circle Line to Tower Hilll.

Not that Mr Campbell was perturbed by his Tube failiings.

"The trouble is when you ask these questions they are so easy to answer. These are things that are so easy to kind of learn but what London wants is people with ideas and the willpower to get things through.