The fourth generation of a family behind one of the most successful farm-based enterprises in the North has unveiled a plan to launch a museum celebrating farming, local enterprise and detailing its remarkable expansion.

Richmondshire councillors are set to decide over the latest diversification scheme at Washfold Farm, near Leyburn, which has gone from having one worker and 18 cows to the area’s largest employer with more than 200 staff since it was established there by the Metcalfe family during the Second World War.

The area of farmland has been intensively used from the late medieval period onwards, and there is a scheduled monument settlement and prehistoric hut circle settlement just 870m north east of Washfold Farm, known locally as Old Bellerby or T’old Ruins.

In documents submitted to the district council, agents for the Metcalfes said they wanted to build staff offices and a museum on the site, which is the base for several enterprises such as a heavy haulage firm alongside a 1,300 pedigree Holstein dairy herd and 1,100 sheep.

The large farm complex is located within open countryside around numerous buildings, and as the site area is about 7,780 square metres it is classed as a major development.

The application states the family wants a central custom-built space for its staff as its office spaces are spread out, crowded and with inefficient flow and poor access. The proposal also states the firm needs capacity at the offices to support future growth.

As part of the proposal there is also an area to showcase the history and development of the farm and the business, to be used by visitors and employees “to understand the history of the business and its evolution”.

The scheme, which has been backed by Leyburn Town Council, would also see two agricultural buildings, a weighbridge and surface water collection pond, added to numerous planning permissions granted over the years.

They include buildings to house dairy cows for milking, a biodigester, slurry lagoon, conversion of existing building to flats for farm workers, a farm office and large agricultural buildings for parking farm machinery and vehicles.

The new pond is designed to collect “grey water” and also be recycled to be used on the farm for washing machinery, irrigation, stock and controlling dust on site.

An officer’s report to a meeting of the council’s planning committee on Tuesday concludes the proposal would be justified in the countryside location to support the needs of an existing and expanding farm and associated businesses at Washfold Farm.

It states: “The proposal will not significantly harm the character of the countryside, and any harm will be minimised through significant tree planting and landscaping. The proposal will not compromise highway safety, and will be designed not to flood or cause flooding elsewhere.”