Ian, 41, from Cambridge, is a travel photographer and began baking six years ago so his children could have fresh bread to eat.
A former member of Buckingham Palace's Coldstream Guards, a firefighter and a bodybuilder are also in the line up.
The show returns to BBC One on 5 August at 20:00 BST.
The first episode will begin with cake week, and the bakers' first signature challenge will be to make the perfect Madeira cake.
The technical challenge will see them tackle judge Mary Berry's frosted walnut cake - a light sponge sandwiched with buttercream and covered with sweet meringue.
The final showstopper task will be to reinvent the black forest gateau.
Mel Giedroyc and Sue Perkins return to host the show, along with judges Berry and Paul Hollywood.
Some 13.5 million viewers tuned in to watch Nancy Birtwhistle win last year's series.
The Dalai Lama's personal UK photographer is among 12 contestants hoping to be crowned master baker in this year's Great British Bake Off.