On 1 June 1987 Janvrin was recruited as Press Secretary to The Queen, though it was initially thought that he would be appointed Assistant Press Secretary. On 19 October 1990 he became Assistant Private Secretary to The Queen, and in 1996 the Deputy Private Secretary. He was promoted a Commander of the Royal Victorian Order in the 1994 New Year Honours, a Companion of the Order of the Bath in the 1997 New Year Honours, and a Knight Commander of the Royal Victorian Order in the 1998 New Year Honours. In February 1999 he succeeded Sir Robert Fellowes (later Lord Fellowes) as Private Secretary to the Queen. He was promoted to Knight Commander of the Order of the Bath in the 2003 New Year Honours.