Eastercon 2.5, known as Festivention. was held in London over Whitsun 1951. The GoHs were Forrest J Ackerman, Wendayne Ackerman, and Lyell Crane. The committee were E. J. Carnell, Charles Duncombe, A. Vincent Clarke, A. Lovett, F. E. Arnold, James Rattigan, Ken Bulmer, Fred Brown, and Ted Tubb.
Festivention was intended as an international convention. It was held at the normal time for Eastercon in place of it and no Eastercon was officially held that year. The name was a tie-in to the Festival of Britain that year.