Hutchinson’s Pocket Guide for Hampshire and the Isle Of Wight, Wiltshire and Dorset, published in 1939, mentions:
Longleat House, near Warminster, a fine Elizabethan mansion said to be the most ancient regularly built house in the kingdom, is a seat of the marquis of Bath. Erected on the site of an Augustine priory by Sir John Thynne, it took twelve years to complete. John of Padua is traditionally associated with the design of the house, and only the north front has undergone any alteration from that time. The interior of the house is very fine; the park and gardens were remodelled by “Capability” Brown at the end of the eighteenth century. For sixty years afterwards 50,000 trees are said to have been planted annually in the park, which is fifteen miles in circumference. The house is shown to visitors on Mondays and Saturdays, also on Thursdays from April to July.
The fifth Thynne to succeed to Longleat married Lady Elizabeth, the Percy heiress, whom we encountered at Petworth in Sussex. But the lady, then only fifteen years old, refused to live with her husband, who shortly afterwards (1682) was found murdered in his coach in London. The property then passed to a cousin, who was created Viscount Weymouth. The marquisate of Bath was conferred in 1789, and the present owner of Longleat is the fifth marquis.