The Duke of Edinburgh will meet Royal Marines who have completed a mammoth 1,664 mile trek today - his final official royal event before he retires from public engagements.
In the grounds of Buckingham Palace Philip will celebrate the achievements of servicemen who have taken part in the 1664 Global Challenge, a series of strength and endurance feats raising funds and awareness for the Royal Marines Charity.
The Queen's Consort announced in May he would be retiring from royal engagements after more than 65 years supporting the monarch in her role as head of state and attending events for his own charities and organisations.
Philip, 96, was praised at the time for his public service with Prime Minister Theresa May leading the tributes saying he had given the Queen "steadfast support'', while Labour leader Jeremy Corbyn said the Duke's ''clear sense of public duty'' had inspired people for more than 60 years.
Here's a look at his royal service in numbers from 1952 to August 2 2017:
22,219 - Solo engagements
637 - Solo overseas visits, including 229 visits to 67 Commonwealth countries, and 408 visits to 76 other countries
5,496 - Speeches given
785 - Patronages
54 - Presentation of colours
32 - Service appointments
14 - Books authored
Despite his age Philip's decision - which was fully supported by the Queen and was not medically related - came as a surprise as he still appeared to relish meeting people and carrying out his public role.
The Duke is known for his quips and over the past few months has been joking about his impending retirement, even telling celebrity cook Prue Leith at a Palace event "I'm discovering what it's like to be on your last legs".
Buckingham Palace has stressed although the Duke's diary of engagements will come to an end on Wednesday he may decide to attend certain events, alongside the Queen, from time to time.
The Queen's public schedule continues as normal but other members of the Royal Family will step up in support of the monarch in her role as head of state.