McGuigan worked for Boite Postale Limited from 1964 until 1972, when he joined the Diplomatic Service. From 1974-1977 he was 1st Secretary in New Delhi, and then 1978-1981 in Kingston. From 1981-1985 he was in the Permanent Under Secretary of State"s Department of the Foreign and Commonwealth Office.
From 1985 to 1988 he was 1st Secretary in Bridgetown.
From 1989-1993 he was Counsellor in Lagos, and then 1994-196 Kingston. He retired from the Foreign and Commonwealth Office in 1997 and joined the Office of the Princess Royal.
The Household of The Princess Royal provides the administrative support to Her Royal Highness The Princess Royal, daughter of Queen Elizabeth World War II lieutenant is based at Buckingham Palace, and is headed by the Private Secretary. The Household is separate from the Royal Household and is funded from the Civil List annuity paid to The Princess Royal for her public duties - which is however reimbursed to Her Majesty Treasury by Her Majesty The Queen.