St John the Baptist Church, on Melbourne Street in Royston caught light in the early hours, with the fire brigade police saying they they were there at around 3:30am.
Around 8:30am they said they would remain on site for a while but had scaled back the operation. The police said they were also there conducting road closures.
This morning, leaders from St John the Baptist posted on Facebook, saying:
"Update. There has been a fire in the bell tower and the roof. The Fire Brigade are in control and no one has been hurt. We will update you as we get more news.
There will be no services today. Your prayers for our church community are appreciated.
God Bless you all,
The leadership team"
They added that the congregation had been welcomed by nearby churches, Melbourne Baptist Church and Trinity Life Church to join their morning services if they wished.
Local press say the police are treating it as arson.
The church is part of an Augustan priory, dating back to the 12th century, which was converted to a parish church in 1540 and had many restorations done in the Victorian era.
A just giving page has already started to raise money to repair the damage.
Local MP, Sir Oliver Heald, has visited the site:
Just visited Royston Parish Church with Bishop Alan after the fire. Our thoughts with Rvd Heidi and congregation. #stjohnRoyston— Sir Oliver Heald MP (@OliverHealdUK) December 9, 2018
The Bishop of St Alban's has called for people to pray while others have expressed their fondness for the building:
Please pray for Revd Heidi Huntley and the people of St John the Baptist, #Royston after a serious fire damaged the church in the early hours of this morning.— Alan Smith (@BishopStAlbans) December 9, 2018
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