Complex sentence: McGrigor became First Sea Lord and Chief of Naval Staff on 20 December 1951 and, having attended the funeral of King George VI in February 1952, he was appointed First and Principal Naval Aide-de-Camp to the Queen in 1 April 1952.
Split into simpler sentences: McGrigor became First Sea Lord and Chief of Naval Staff on 20 December 1951. He attended the funeral of King George VI in February 1952 and was appointed First and Principal Naval Aide-de-Camp to the Queen in 1 April 1952.