Mr Valentine, the last known surviving light bomber pilot from the Normandy landings, lived out his final 27 years in Hethe, near Bicester.
Last night he was praised by Mr Cameron as “an extraordinary man who displayed extraordinary bravery”.
Mr Valentine met the Prime Minister just 16 months ago when he presented the ex-pilot with a Defence Medal at Downing Street, for his service in France with the Highland Light Infantry.
Mr Cameron said: “I had the honour of presenting Mr Valentine with the Defence Medal in recognition of the unique contribution he and others made protecting Britain. I was saddened to hear about his death and my thoughts are with his family at this difficult time.”
Banbury MP Sir Tony also paid tribute and said the death of the last Second World War veteran should serve as “a reminder to us all”.