Downing Court, opened in 1976, was operated by East Cambridgeshire District Council until they transferred their housing stock to Hereward Housing of Ely in 1993.
Now there are 20 bungalows in Downing Court and a further 19 bungalows in the adjacent Vicarage Close which make up the scheme run by Hereward.
Scheme manager Debbie Bull decided to organise the birthday celebrations after being approached by residents, and Hereward Chief Executive Nick Abbey planted the tree.
Josie Chalkin, the first warden (as they were then called) when Downing Court originally opened, was among the guests as well as the longest serving resident Irene Stepney who moved into her bungalow in 1984.
Film and quiz nights, bingo, keep fit sessions and a lunch club are among the regular activities at Downing Court and guest speakers are also invited.
Debbie said: “We always welcome villagers from Swaffham Bulbeck here to join in our activities because we are all part of the same village community.”
Refreshments, games and entertainment were all arranged to make the birthday celebrations go with a swing.