Stables and a passageway used as a wood store were destroyed in the blaze and a large area of roof was badly damaged at the farm, which is at the hub of the Cowdray Estate’s farming enterprise.

Herdsman Peter Waker raised the alarm at 5am and woke colleagues to help him move 33 cows from a building behind the fire-stricken area.

“They were right behind it, bedded down on straw with tiles falling from the roof. We got them out and into a field,” Mr Waker said.

The cows are ‘dry’ and not currently in the milking herd, which Mr Waker was preparing to milk in the dairy, a separate building.

He said: “I checked them first and they were fine, so I went off to get the other cows ready for milking. Then I heard popping and banging and saw flames and sparks coming from the roof of the other building.

“I phoned the fire brigade and woke up some other people to help me get the dry cows out. When we went round to the other side of the building, the roof was gone and flames were going straight into the sky. Once the fire brigade arrived and had things under control I got on with the milking.”

Five fire crews from Midhurst, Petworth and Haslemere spent nearly six hours at the scene. West Sussex Fire and Rescue Service said the roof of the affected building, measuring 60m by 20m, was well alight when they arrived.

A spokesman said: “One hundred per cent of the centre of the stables and woodstore was damaged and about 40 per cent of the roof.”

Recently-baled hay stored in the stables is suspected to have overheated and caused the blaze.