Britain's 96-year-old Prince Philip carried out his final solo engagement here to begin his retirement from royal duties.

The Duke of Edinburgh is the longest serving consort to a British monarch with 65 years of public service and appearing at hundreds of events alongside his wife Queen Elizabeth II.

His appearance on Wednesday at a parade to mark the finale of the 1664 Global Challenge a series of strength and endurance challenges raising funds and awareness for charity brings his solo engagements total to 22,220 since 1952.

In his role as Captain General of the Royal Marines, he met British naval servicemen who have taken part in a 1,664-mile trek as part of the challenge at a Buckingham Palace ceremony.

Prince Philip then took the royal salute from a dais on the Palace forecourt and parade ended with three cheers for the Captain General.

He then set off to join the Queen at Balmoral Castle in Scotland, where the couple traditionally spend this time of the year.

While his official diary of engagements come to an end on Wednesday, the Palace has said the Duke may still decide to attend some events alongside the Queen, 91, whose diary of events remains unchanged.

"The parade would bring His Royal Highness' individual programme to a conclusion, although he may choose to attend certain events, alongside the Queen, from time to time," a Buckingham Palace spokesperson said.

According to palace records, Prince Philip has undertaken 637 solo overseas visits to 143 countries, delivered 5,496 speeches, written 14 books and carried out the role of patron for 785 organisations during his royal career.

It was announced in May that he would no longer undertake any solo royal engagements but the Palace had stressed that the surprise news was not health related.

The Duke is known for his quips and over the past few months has been joking about his impending retirement, telling British celebrity cook Prue Leith at a Palace event: "I'm discovering what it's like to be on your last legs".

Prince Philip, who has long been considered among the most active royals in the UK, has been married to Queen Elizabeth II since 1947.

The couple are set to mark their 70th or platinum wedding anniversary in November this year.

Their son and heir, Prince Charles, and grandsons Princes William and Harry are expected to take on additional royal duties to step in for Prince Philip at public engagements from this month.

The Queen and Prince Philip had already cut down on long-haul travel for some years now, with younger royals taking on those duties.

Close confidantes of the royal family said that the decision to retire was a personal one taken by Prince Philip himself, who may now devote his time to writing his memoirs.