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Buster Martin's claim to be the oldest London Marathon runner, at 101, has not been approved by the Guinness Book of Records. So how does it verify age-related records?
Running 26 miles aged 94 is an extraordinary feat. But for Buster Martin, who says he is 101, the accolades have been clouded by questions about how old he really is.
The Guinness Book of Records has not received the required proof, it says, and an NHS record says he is in fact 94.
Officially the oldest marathon runner is a Greek man who was 98 when he ran one in Athens in 1976.
Guinness Book of Records requires at least a birth certificate but checks other documents like marriage certificates and evidence of military service
But Mr Martin is not the only person to have had his age scrutinised after apparently rolling back the years to make sporting history.
Cameroon striker Roger Milla was confirmed as the oldest World Cup scorer, aged 42 in 1994, but some suspected he was in fact even older.
So how is age verified for potential record holders?
For people born in the UK, a birth certificate is the most reliable document. All births must be registered within 42 days, either at the hospital or the local register office.
Copies of birth certificates can be bought online, by post or by telephone, or through the register office where the birth was registered.
But for those born abroad - Mr Martin says he was born in France - it can get more complicated.
The Guinness Book of Records uses a gerontologist - someone who studies aging - based in the US to verify all age-related record claims by scouring the globe looking at other evidence.
Birth certificates can provide a shock
"For all cases, even for those people who have provided a birth certificate, we cross-reference and look back at a marriage certificate, the date they got married and if they had children, the date they had children, or military service, to make sure it's all verified," says a spokeswoman.
"In the absence of a birth certificate they will look at all these to verify age and occasionally pension policies. But a birth certificate is the best proof."
A UK birth certificate would probably be enough to claim a world record but other checks would be done too.
NHS cards are not accepted, she says, because the date of birth is supplied by the patient. In Mr Martin's case, Guinness says he gave the NHS two dates of birth, one which made him 94 and the other 101.
The rest of the evidence Mr Martin gave to Guinness, such as marriage and children, could not be verified.
But the Londoner told BBC Radio 5 Live: "I'm 101. End of story. And that I'll stick to because I know how old I am."
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For people who are born outside the UK, it is possible to obtain official documents such as a National Insurance number (NINO) without a birth certificate.
"No one piece of documentation on its own establishes a person's identity," says a spokeswoman for the Department of Work and Pensions.
"The NINO allocation process involves checking the customer's background and circumstances in order to build a complete picture of the customer."
As many documents as possible are requested, including passport, national identity card, marriage certificate and full driving licence.
NINOs are automatically issued for people who have been subject to child benefit claimants in the UK.