Duke's collision sparks debate on whether he is too old to drive at 97

When the Obamas visited the UK for a state visit in 2016, they weren't escorted from their helicopter by a security driver.

Instead, the task fell to Prince Philip - a keen motorist. The Duke of Edinburgh, 94 at the time, gave the Queen and the world's most powerful couple a lift to Windsor Castle.

Mr Obama was complimentary about the duke's driving skills, and said at the time: "I have to say I have never been driven by a Duke of Edinburgh before and I can report that it was very smooth riding."

But three years on, questions are now being raised as to whether Prince Philip should still be driving at the age of 97 after he was involved in a car crash while behind the wheel near the Sandringham Estate.

Royal biographer Penny Junor told Sky News: "It was a horrible thing to happen, but should he be driving?

"I have no idea who the fault lay with - but he is 97 years old and maybe his reactions are not as fast as they once were."

While there is no legal limit on driving ages in the UK, motorists have to renew their licence at least 90 days before reaching the age of 70, and then every three years after that.

A licence can only be renewed if the minimum eyesight requirement is met and there is no other reason to prevent a person from driving.

DVLA figures from 2017 show that 100,281 people over the age of 90 hold valid licences, while 248 people over 100 years old have a licence.

Robert Jobson, royal editor of the Evening Standard, said: "It's miraculous that he - a 97-year-old man - walked away from this."

He felt Prince Philip should "probably not" get behind the wheel given his bodyguard would be an experienced driver.

He added: "It seems rather ridiculous to put, not necessarily himself, but other people at risk.

"I think there will be some people close to him in the family, suggesting that maybe it's better he's driven.

"Nobody wants to see a situation like this."

Chris Musselwhite, associate professor at Swansea University's Centre for Innovative Ageing, told Sky News: "We tend to find, as a cohort, we don't think older drivers are any more dangerous than perhaps any other age.

"On the whole we think the older cohort are pretty safe."

Pete Williams of the RAC said: "I think the majority of older drivers are quite good at restricting and limiting their own driving when they find certain circumstances more difficult. Many people will not drive at night, perhaps just stick to local roads.

"The evidence isn't there that older drivers are any greater risk."

Edmund King, president of the AA, said calls for elderly drivers to face bans or restrictions after car crashes are misplaced.

He said: "We wish the Duke of Edinburgh well. Many commentators use high-profile car crashes involving elderly drivers as a reason to call for bans or restrictions on older drivers.

"If driving restrictions based on age and safety were introduced we would be more likely to restrict young drivers rather than older drivers.

"Young, predominantly male, drivers are much more likely to crash within six months of passing their test than older drivers within six months of hanging up their keys.

"Older drivers often self-restrict their driving by not driving at night and only driving on familiar roads."

Age UK said deciding to stop driving can be difficult but it does not have to mean the end of a person's independence or mobility.

The charity says on its website: "If you've decided to stop driving, or been advised to by the DVLA, there are many ways you can get around and there may be help with transport costs."