Fire crews tackling are fire at a Grade 1 listed house are using water from a nearby lake.
The roof of 17th century building is close to collapse.
More top news
Military personnel are unlikely to be deployed on the streets of Avon and Somerset despite an increase in the national terror threat level.
The major party leaders' campaigns for the General Election will remain suspended on Wednesday following the Manchester terror attack.
The threat level has been raised to critical by MI5's Counter-Terrorism Analysis Centre.