Controversial director Roman Polanski's gripping political thriller The Ghost makes timely viewing as the country prepares to elect a new government.

Author Robert Harris' story about an unrepentant former British Prime Minister being threatened with war crimes charges after leading the country to Middle Eastern conflict has drawn inevitable comparisons to Tony Blair's invasion of Iraq.

And with Polanski editing the film while under Swiss house arrest awaiting extradition to the US for alleged sex with a minor, this film had already had its fair share of scrutiny before cinema-goers even got to digest it.

Luckily The Ghost impresses on its own merits. Polanski's storytelling echoes the suspense of a Hitchcock classic with overcast skies, deserted beaches and sterile properties adding to the sense of foreboding and isolation.

Ewan McGregor gives his finest performance in years as the new ghost writer signed up to pen the memoirs of the charismatic but hated former premier Adam Lang, played by Pierce Brosnan.

Once in situ at Lang’s clinical Cape Cod HQ, the ghost, as he is referred to throughout, discovers his predecessor was washed up on a beach days earlier and somehow his supposed suicide just doesn’t add up.

Usually notorious for his array of dreadful big screen accents, McGregor convinces as a Londoner who, far from home, finds himself well out of his depth when he starts to uncover information linking the former PM with the CIA.

The tension builds up nicely as the ghost realises he is in imminent danger and finds it increasingly difficult to know who he can trust.

Lang’s super efficient assistant Amelia (Kim Cattrall) is ruled out as she appears to have total loyalty to her boss so he confides his suspicions to, and falls into the arms of, Lang’s long-suffering wife Ruth, played by the talented Olivia Williams.

The plot twists and turns – with a few red herrings thrown in along the way – and just when we think the danger has passed the ever-skilful Polanski goes in for the kill.

His private life may be marred by controversy but while he is still producing work this good no one could question the 76-year-old’s directorial judgement.