He specialized in collecting the first postage stamps of George V"s reign. He worked as a chartered accountant until he partially retired in late 1992. In September 1996, he was hired as an adjoint to the keeper of the Royal Philatelic Collection, who was Charles Goodwyn.
He helped him accelerate the mounting of the George VI postage stamp collection.
Sefi participated in international philatelic exhibitions of parts of the Royal Collection and in welcoming students and researchers. He played a major role in the move of the collection from Buckingham Palace to Street James"s Palace in the early 2000s.
When Charles Goodwyn announced his retirement in late 2002, Sefi was chosen to succeed him among three other candidates by the Keeper of the Privy Purse. He directed the preparations of The Queen"s Own, a Royal Collection exhibit at the National Postal Museum in Washington, District of Columbia, which was held in 2004.
To assist Sefi, he had the help of Surésh Dhargalkar, an architect and conservation specialist, who was Sefi"s assistant since 1996 and an adjoint to the Keeper in 2003.
To help him for the mounting, he hired George VI specialist, Rod Vousden, as assistant.
He became an active member of the Philatelic Society of Great Britain of which he was president between 2000 and 2002. Sefi later became the president of the Royal Philatelic Society London where he has been a member of many decision-making bodies since 1990.