Metal thieves caused "considerable damage" to the roof of a 13th Century church but were disturbed before they could flee with the haul of lead.
Urgent measures have been taken to make the Church of St Peter and St Paul in South Petherton, Somerset, watertight after it was targeted on Thursday.
Churchwarden Steve Harrison went to the church at about 02:00 GMT after taking a call from a concerned neighbour.
The lead had been rolled up and thrown into the churchyard below.
Mr Harrison believes his presence disturbed the thieves but the damage to the roof had allowed rainwater to enter the church.
"It seems they were starting to move it close to the road, presumably for their transport to come and collect it," he said.
"We may well have been able to recover all of the lead and it would be nice to think the thieves left empty-handed, but of course there is considerable damage to the roof."
A spokesman for Avon and Somerset Police said: "It appears the offenders were disturbed and fled the scene.
"We have had a number of reports of similar incidents in Somerset in recent weeks, with churches in areas such as Glastonbury, Kingsbury Episcopi, Barrington, Bridgwater and Ilton also targeted."