A Dunkirk veteran, who is celebrating his 105th birthday, is "probably more alert than most people half his age", his friend has said.
John Hamilton, who was part of the British Army told to evacuate from Dunkirk in May 1940, is having a party with family and friends.
Adela Forestier-Walker said he still "reads voraciously" and had an "incredible memory".
Mr Hamilton's former school, Clifton College, will fly a flag in his honour.
Members of his regiment will be present.
Mr Hamilton, previously told the BBC he had "clear as bell" memories of the three days his battery defended retreating troops from aerial attacks by German Stuka bombers.