Given the following context:

The house has been restored and preserved as it looked in the 1920-30s; at the time of the Trust's purchase, Churchill committed to leave it, "garnished and furnished so as to be of interest to the public". Rooms are decorated with memorabilia and gifts, the original furniture and books, as well as honours and medals that Churchill received. Lady Churchill's long-time secretary, Grace Hamblin, was appointed the first administrator of the house. Earlier in her career, Miss Hamblin had undertaken the destruction of the portrait of Churchill painted by Graham Sutherland. The picture, a gift from both Houses of Parliament on Churchill's 80th birthday in 1954, was loathed by both Churchill and Lady Churchill and had been stored in the cellars at Chartwell before being burnt in secret.The opening of the house required the construction of facilities for visitors and a restaurant was designed by Philip Jebb, and built to the north of the house, along with a shop and ticket office. Alterations have also been made to the gardens, for ease of access and of maintenance. In 1987, the Great Storm caused considerable damage, with some twenty-three trees being blown down in the gardens. Greater loss occurred in the woodlands surrounding the house, which lost over 70% of its trees.Chartwell has become among the National Trust's most popular properties; in 2016 some 232,000 visitors came to the house. In that year, the fiftieth anniversary of the house's opening, the Trust launched the Churchill's Chartwell Appeal, to raise £7.1M for the purchase of hundreds of personal items held at Chartwell on loan from the Churchill family. The items available to the Trust include Churchill's Nobel Prize in Literature awarded to him in 1953. The citation for the award reads, "for his mastery of historical and biographical description as well as for brilliant oratory in defending exalted human values". The medal is displayed in the museum room on the first floor of Chartwell, at the opposite end of the house to the study, the room where, in...

answer the following question:

What is the full name of the person earlier in whose career had undertaken the destruction of the portrait of Churchill? 

Grace Hamblin