Cracks in the tower at St Jude's in Hampstead Garden Suburb mean the church's parish council now need to raise an extra £60,000 for essential work on the "highly vulnerable" building.
When scaffolding was erected and preliminary work began ahead of the replacement of the church's weather vane earlier this year, engineers were shocked to discover serious structural issues and cracks in the brickwork of the Grade-I listed building - designed by the great Sir Edwin Lutyens.
The weather vane had been blown off the tower in 2016 during Storm Barney.
The work to remedy this is expensive, and the church's parochial council is now reviving its fundraising campaign, having already raised around £50,000 from generous community groups and individuals.
As it has the scaffolding up around the tower at the moment - paid for by insurers as part of the previously-planned repairs - it has a limited window to get the vital work done as affordably as possible.
"We can't lose this opportunity," said David White who chairs the parish's restoration steering committee and is in charge of the project.
Father Alan Walker, the church vicar, told this newspaper: "The thing is that, like most church communities, we have inherited a building from the past, and ours is a Grade-I listed building that has to be protected and maintained in a very specific way.
"We are totally dependent on grants, gifts and fundraising.
"It's a massive building in terms of its scale. In a sense that's one of things the architect Lutyens had in mind in Hampstead Garden Suburb - the church spire draws people from a distance."
David continued: "We had raised all the money necessary but now the costs have substantially risen."
The church has produced a series of exhibition boards explaining the scale of the problem, and these will be in place at the church
The exhibition explains: "Whilst Lutyens’ church is an architectural masterpiece, it is something of a miracle that this part of it is still standing."
The issue - discovered when the engineering team and architect inspected the century-old brickwork - is that because of the method of building employed by Lutyens, there is a fundamental weakness in the construction and a lack of "bonding".
To contribute to the church's campaign, visit stjudeonthehill.com/restoration-appeal or head to St Jude's itself to see the exhibition.
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