Kenwood House, built 1764-79 by Robert Adam for the 1st Earl of Mansfield, whose decision, in the 1771 Somerset case, was an important step towards the abolition of slavery in the British Empire. Threatened with development in the 1920s, it was bought in 1925 by Edward Cecil Guinness, 1st Earl of Iveagh, and donated to the public. It is now managed by English Heritage. The magnificent house, priceless art collection and 74-acre estate are open free of charge; see their website for opening times.