Older brother of actress Lizzy McInnerny.
Is an Oxford (Wadham College) graduate.
After playing an essentially similar character called "Percy" in each of the first two "Black Adder" series, he declined to reprise the character in Blackadder the Third (1987), as he felt that the possibilities of playing a bumbling fool had been exhausted. After playing a guest role in one episode of the third series, writers Richard Curtis and Ben Elton persuaded him back into the regular cast for Blackadder Goes Forth (1989) by offering him a role with a different name (and personality) in the shape of "Captain Darling". He is, thus, the only one of the cast to play differently named regular characters in different series.
Along with Rowan Atkinson and Tony Robinson, he is one of only three actors to appear in all four "Blackadder" series: Blackadder (1982), Blackadder II (1986), Blackadder the Third (1987) and Blackadder Goes Forth (1989).
Long-term partner is art director Annie Gosney.