SITTING elegantly at the top of Georgian Lemon Street with its distinctive cupola, the church of St John the Evangelist oversees Truro’s biggest parish and at 400 boasts the second largest capacity in the city after Truro Cathedral.

Yet it’s easy to walk past the front door without an inkling as to the space and treasures within.

“It’s quite the Tardis – you don’t see how magnificent it is from the outside,” says churchwarden Sarah Peters. “Not everyone realises it’s a church because it doesn’t have a spire or tower – we are a bit different.”

St John’s Church is spiritual home to Archbishop Benson CofE Primary School as well as Truro High Schools. Its fine acoustics make it a popular music venue – The Sixteen ran a secondary school workshop there before last week’s cathedral performance, and look out for the opening concert in IMS Prussia Cove’s autumn tour this Sunday [September 28] at 2.30pm, with a programme of Beethoven, Dvorak and Grieg.

Truro's growing prosperity in the 18th and 19th centuries saw the existing churches of Kenwyn and St Mary's reach full capacity. St John’s was built in 1828 to the designs of architect Philip Sambell, who was also behind the Lander monument, Strangways Terrace, the Wesleyan Chapel and Truro Savings Bank – better known today as Cornwall Museum and Art Gallery in River Street.

With its Italian-style curved apse, carved wood ceiling and cupola, the Grade II listed building exudes an exotic glamour, although its upper balconies are more reminiscent of Cornwall’s Methodist chapels.

There are future plans to make the seating more flexible. “These aren’t the original pews, and they are of no real architectural importance,” says Sarah. “With modern seating, we can make more space for community events like Messy Church.”

But St John’s needs some TLC to fix the kind of problems afflicting so many churches. A crowdfunding campaign has been launched to tackle a dry rot infestation, with £4,000 raised towards a total of £11,000 in just two weeks (further boosted by a £2,500 from Cornwall Historic Churches Trust).

Once that has been achieved, attention will turn to black mould in the cupola, woodworm under the organ and blocked guttering.

“If anyone in Truro or even Cornwall feels it appropriate to give a gift to the church, please bear us in mind,” said treasurer Paul Cherry.

A fundraising schedule of cake stalls, coffee mornings and quiz nights (the next one is on October 11) takes place in the church hall. It’s also a popular venue for children’s groups and home to Truro Homeless Action Group’s daily cooked breakfasts.

When St Paul’s Church on Tregolls Road closed in 2008, its parish was absorbed into St John’s. With St Paul’s demolition recently confirmed by Church Commissioners, St John’s plans to hold a service of thanksgiving for its sister church, while reminding worshippers of its warm welcome.

“We encourage people to come and have a look and meet us,” said Sarah. “This is your parish church.”

Donations can be made at givealittle.co/c/StJohnsTruro