Perhaps the most outstanding of Campbell’s farm buildings is the magnificent cast-on-site mass-walled concrete barn in Buscot village, still used today for grain and machinery storage. It pre-dates other known concrete farm buildings by about thirty years, having been built around 1870. Measuring 60ft x 162ft x 12ft 6in. to the eaves, its concrete walls are 1ft 4in. thick at the base. The roof is in red double roman tiles and is lined on the inside with tongue-and-groove boarding. The gable ends are red Bridgwater bricks.
  
Adjacent to the concrete barn is part of the cattle sheds, also in red brick and roman tile, as were the majority of Campbell’s buildings. At Kilmester Farm there are a number of smaller concrete-walled, roman-tiled buildings that can also be attributed to Campbell.

The buildings from this period are in the style of the Bridgwater area of Somerset, suggesting that a builder or architect from that area was used. This is further strengthened by the Berks and Oxon directory of 1863 giving ‘Simmonds and Coulhurst’ as the proprietors of ‘The Estate Brick and Tile Works’ at Eaton Hastings. The Coulhurst family are well-known Somerset builders and builders’ merchants.

One of the storerooms at Oldfield Farm has revealed some items of telegraph equipment, which, when dated, may prove a link with the estate telegraph of the 1870s.