 In 1939 Sir Cennydd Traherne leased the Dyffryn House and Gardens to Glamorgan County Council, as a botanical garden on a 999-year lease.In 1973, the gardens were used as the venue to host a garden party to commemorate the dissolution of Glamorgan County Council.In 1995 Sir Cennydd Traherne died, and in 1999 his nephew Councillor Rhodri Llewellyn Traherne sold the freehold of Dyffryn House and Gardens to the Vale of Glamorgan for the sum of £300,000.