There were no bishops, not even a poor parson, to bless the event or platitudinise amiably over the cake stalls, the bowling alley, and the jazz band and firework show set up on a steep meadow falling away below the mission's rusting walls.
Instead, there was Lady Margaret Oswick, a street performer better known in Bath and abroad as Ralph Oswick, of the city's Natural Theatre Company. Cheered by a crowd of 500, Lady Margaret swept up the narrow approach of Bailbrook Lane in a blue Rolls-Royce to declare the fete open. Eulogising on 'Our Lady of the Crinkly Tins', Lady Margaret proclaimed from the poems of Patience Strong, then mounted a ladder set against the mission's 30ft (9m) tower, lifted its old tin lid and released 1,000 balloons into the hot Avon sky. Vince Parker, 52, a jazz man who played the mission's hand- pumped organ in its heyday, led his quintet in a rousing chorus of 'Happy birthday dear tin church'.
Even in a city renowned for its architectural causes, the preservation of Bailbrook's corrugated iron mission - built in 1892 from a mail-order kit to rescue Robertson's jam orchard workers from their unsociable ways - has touched a chord in conservationists' hearts.
The building was bought and occupied 15 years ago by Graham Boys, 48, an alternative theatre veteran who bought it for pounds 1,500 from the last vicar when it was shut as a church. Regarded with initial suspicion in a lane of Grade II listed Georgian cottages, Mr Boys won the community's confidence with his neighbourly manners and two cats, Mostly Black and Mainly White. Neighbours were impressed by his efforts to stop the mission blowing off the hill during storms; he spent one night holding a window against the gales with a broom, praying as he listened to its glass cracking and roof sheets lifting away.
Now, with the help of Michael Trevallion, an architect who specialises in restoration, he has begun a campaign to persuade planners that the mission is worth listing as a rare survivor of Victorian kit construction. Bath City Council, which once wanted to demolish it, has now agreed to let him live there and run an arts studio, provided he makes the building safe and sound. He has an appointment with a broker this week and is confident he can raise a pounds 25,000 mortgage to replace the old tin sheeting and restore the mission to its Victorian glory. 'Two people came down from the Department of the Environment three weeks ago and were very impressed,' Mr Boys said yesterday. 'They said it was certainly out of the general run of tin churches and well worth listing. I'm expecting to hear from them any day now. Doing it up means I've got to say goodbye to the church as a genuine decrepit building, but that's the problem. It's only a rusty old thing on its last legs. If I don't rebuild it soon, it'll blow away any day now.'