Haggard was born in London but grew up on a small farm in Clackmannanshire. He is the great-great-nephew of H. Rider Haggard, and is the son of the actor, poet and novelist Stephen Haggard who died in 1943. Haggard is married to stained glass artist Anna Sklovsky, with whom he has two children, the actress Daisy Haggard, and William Haggard who is an architect. He has four children by his first marriage, Sarah, Claire, Rachel and Philip.
Haggard began his career as an assistant director at the Royal Court in 1960, then directed at Dundee Rep and Glasgow Citizens before joining the first National Theatre company in 1963 where he co-directed (John Dexter and Bill Gaskill) and assisted Laurence Olivier and Franco Zeffirelli.
In 1965 he moved to BBC Television, directing plays for the anthology drama series Thirty-Minute Theatre in the 1960s, later working on the more prestigious anthology shows, Callan, Public Eye, Armchair Theatre (for ITV) and Play for Today (for the BBC). He directed for a variety of programmes throughout the 1970s, such as The Rivals of Sherlock Holmes, The Love School, Love for Lydia and The Chester Cycle of Mystery Plays (1976).
Probably his best-known work came later in the decade. In 1978 he was the director of Dennis Potter's landmark drama serial Pennies From Heaven for the BBC, for which he received a BAFTA Award.The following year he directed the ambitious science-fiction serial Quatermass, a Euston Films production for Thames Television, shown on the ITV network. Both of these productions are available on DVD, and the Pennies From Heaven release includes an audio commentary from Haggard. His audio commentary on Venom is well known for its forthrightness, and some hilarious anecdotes on the competitive antics of stars Oliver Read and Klaus Kinski.
His film work includes I Can't... I Can't (1969), cult classic The Blood on Satan's Claw (1970), the cinema version of Quatermass (1980), Summer Story (1988), The Fiendish Plot of Dr. Fu Manchu (1981), Peter Sellars last movie, and Venom (1982). That year he also directed Ticket of Leave Man at the National Theatre.
Later television work included Mrs Reinhardt (1986), a number of US TV Specials with stars such as Liza Minelli, Cheryl Ladd and Judge Reinholdt, the Gerry Anderson science-fiction series Space Precinct (1994) and various one-off TV dramas such as Eskimo Day (1996) Cold Enough For Snow (1997) and The Hunt (2001). The Canadian prairies-set Conquest (1998) was his last feature film. He directed Academy Award winners, Vanessa Redgrave and Maximilian Schell in the 2006 mini-series, The Shell Seekers.
Haggard has also had a 40 year parallel career campaigning for directors’ rights. He was President of The Association of Directors and Producers in 1976; he founded and was first Chairman of the Directors Guild of Great Britain (DGGB,) formed in 1982 at a meeting of over a hundred film, theatre and television directors, many of them world famous, at Ronnie Scott's Club in London. He started the Directors’ and Producers’ Rights Society (DPRS, 1987), serving on its board for 20 years, until it transmuted in 2007 into Directors UK, which he still serves as a Board Member. He was also Vice President and Chairman of FERA, the Association of European film directors from 2010 - 2013.