Guinness World Records says it does not recognise claims that a 100-year-old Briton is the world\'s oldest marathon runner.Fauja Singh, from Ilford, east London, attracted worldwide publicity after he completed the Toronto marathon last week.Guinness World Records says it has not ratified the record as Mr Singh cannot show a birth certificate from 1911.His trainer, Harmander Singh, says such documents were not made in India then.Fauja Singh is said to hold a number of world records, but the BBC\'s 5 live Investigates programme has learned that none of these records has been ratified by Guinness World Records.His British passport, showing his date of birth as being 1 April 1911, as well as a letter from the Queen congratulating Mr Singh on his 100th birthday, have been shown to the organisation. But it says these are not considered sufficient proof of age.A letter from Indian government officials stating that no birth records were kept in 1911, and a statement from a former neighbour in India, have also been passed to Guinness World Records, but the organisation says these too are not evidence enough.Fauja Singh recently completed the Toronto Waterfront Marathon in eight hours, 25 minutes and 16 seconds, finishing in 3,850th place, ahead of five other competitors.He received worldwide publicity celebrating his position as the oldest man to complete a marathon - numerous media organisations, including the BBC, announced he had made it into Guinness World Records.It has also been widely reported that Mr Singh already had a place in Guinness World Records for the over-90 marathon category after running the 2003 Toronto marathon in five hours and 40 minutes.But Guinness World Records has in fact not ratified this record, although Mr Singh is listed as a record holder for this performance on the World Masters Athletics website - an organisation which accepts a passport as a proof-of-age document.