Toby Smith, who was keyboardist and lead songwriter for the band between 1992 and 2001, co-wrote hits including Emergency on Planet Earth, Virtual Insanity and Deeper Underground. He will conduct the official opening of the fair at noon.
Visitors can enjoy the crowning of the May Queen, traditional May pole dancing by children from St Loys School, displays by the Brackley Morris Men, and performances by Brackley and District Brass Band.
Other attractions include arts and crafts activities, side shows, stalls, rural displays, live music, terrier racing, a classic car display, and a grand raffle with prizes including a three-day pass to the 2009 British Grand Prix at Silverstone.
The popular Great Weston Five Mile Race will set off from the fairground at 10am. Refreshments will be available all day.
Entry is £1.50 for adults and 50p for children. Car parking at the fairground in Helmdon Road, Weston, is free-of-charge.