Simplify the following text for a Grade 7 native English-speaking person.
Original: The Hon . Gerald Lascelles , younger son of Mary , the Princess Royal ( daughter of King George V ) was the tenant 1956-1975 , on a 99 year lease , and restored the gardens ( adding a swimming pool , and tennis court ) .
Simplified: The Hon . Gerald Lascelles , younger son of Mary , the Princess Royal ( daughter of King George V ) was the tenant 1956-1975 , on a 99 year lease . He restored the gardens , and added a swimming pool , and tennis court .