Among those invited to the garden party on Tuesday were landlords of the New Inn pub in Buckingham, Mike and Deirdre Hall, and members of the Normandy Veterans' Association.
Mr Hall said: "We were invited because of our public duties' work and work for charities. In my case it was for my work with the probation services in the mid-60s."
During that time Mr Hall was working for a window company in Kent. He also helped find employment for youths put forward by the probation service.
He added: "I managed to speak with the Duke of Edinburgh which was quite a thrill as he is one of my semi-heroes anyway.
"He talked to us about the things we had done and was a very personable man.
"It is quite a humbling experience really and one which makes you feel appreciated."
Mr Hall's wife, Deirdre was invited because of her work as a teacher and other community activities. She managed to speak briefly with Baroness Thatcher, but added: "It was the aspect of meeting people from different parts of the country and different backgrounds, all with such interesting stories, that was the best part."
Dunkirk veterans Thomas Inns, of Moreton Road, Buckingham, and William Grantham, of Bridgewater Road, Brackley, were invited for their involvement with the Aylesbury branch of the Normandy Veterans' Association.
Mr Inns said: "I had a talk for a few minutes with Prince Philip about when we went to Normandy this year to visit the war cemeteries. He was very interested in that and it was a very nice day."
Mr Grantham added: "It was certainly an honour and it was especially nice speaking to the Duke and seeing the Queen."
Each guest received a certificate and the veterans also received special lapel badges.