Church officials say it will take six months to restore an ancient church after a blaze caused more than £500,000-worth of damage.
Arsonists are believed to have set light to the 12th Century St Mary's and St Peter's Church in Wilmington, destroying a Victorian organ, the vestry and roof.
Church leaders in the village, near Polegate, said the building attracted thousands of visitors each year.
Tourists also flock to see the Long Man of Wilmington, the chalk carving in the side of the Downs between Lewes and Eastbourne.
Parish council treasurer John Marshall said: "The church is a focal point for those who worship and also for those who do not come to church regularly.
"When something like this happens, everyone in the village knows about it. It's a very tight community."
Police have appealed for witnesses, particularly three American tourists who told a parishioner about a man acting suspiciously on Sunday.
Detective Constable Jason Finch, leading the arson investigation, said: "I want to stress that these people are not suspects.
"We believe they had a camcorder so it is possible they have information which could hold the key to the investigation.
"This was an ancient church which, until now, has taken pride of place at the centre of this small community.
"We are appealing for anyone who was in Wilmington, particularly near the church between noon and 4pm, to call us if they recall seeing anyone acting suspiciously."
Anyone with information is asked to call Mr Finch on 0845 6070999 or Crimestoppers in confidence on 0800 555111.
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