The Ghost, Roman Polanski, 127 mins, (15)City of Life and Death, Lu Chuan, 136 mins, (15)

Robert Harris's story of a former PM accused of war crimes is already losing its lustre of topicality

Although Roman Polanski's new thriller doesn't exactly crackle with up-to-the-minute urgency, it does have a certain gossipy timeliness – though perhaps not as much as it did in February, when it premiered at the Berlin Film Festival.

Tony Blair – on whom one character might or might not be "based", if it please the court – had just appeared before the Chilcot inquiry on Iraq. And Polanski himself had recently been placed under house arrest in Switzerland, pending a decision on whether or not he'd return to the United States to face his long-standing legal issues. If the spectre of Polanski's 1970s sexual misdemeanours hadn't been hovering, I doubt The Ghost would have been quite such news: the attention it drew in Berlin is testimony to the PR value of a director not turning up to promote his own film.

For British audiences, there's a special curiosity value to The Ghost, which was jointly adapted by Robert Harris from his own novel. In this political mystery-à-clef, Ewan McGregor plays a journalist who signs on to polish the memoirs of former British PM Adam Lang (Pierce Brosnan) after a previous ghost writer has met a mysterious end. McGregor flies to an island on America's East Coast, where he sits down to grapple with Lang's blandly indigestible slab of text. He must also grapple with the ego of the charismatic Lang – played by Brosnan not as a smiley Tony-clone, more as a raffish, volatile matinee idol. Meanwhile, controversy is hotting up over Lang's complicity with US renditions of suspected terrorists, and on the sidelines, Lang's wife Ruth (Olivia Williams) is bitterly grinding her teeth – which are altogether unlike Cherie Blair's – over her living conditions ("It's like living with Napoleon on St Helena").

The Ghost is a polished entertainment, with a modicum of racy edge and much ominous atmosphere, German locations standing in for the rain-soaked Eastern seaboard. Harris's plotting provides some taut Hitchcockian business: in the cleverest sequence, satnav gives McGregor the wherewithal to follow his predecessor's ghostly path. There are some juicy performances: among them Tom Wilkinson, that master of the cagily respectable; Kim Cattrall, crisply modelling a glassy English accent; the rarely-spotted veteran Eli Wallach; and, grabbing the film with both hands, a superb Olivia Williams, spiky and knowing.

Blair allusions notwithstanding, you'll spot certain parallels with Polanski's own situation. Facing the prospect of war crimes charges, Lang moans that he may never again be able to leave the US; Polanski has long been unable to set foot there. Lang is temporarily exiled in a luxury villa, but Polanski can't have anticipated himself languishing behind locked doors in Gstaad. So it goes.

Still, these anecdotal points of interest don't in themselves make The Ghost any more substantial. The film starts off drab and fusty – a scene featuring a tweedy old-school publisher suggests that Polanski isn't getting out much these days, but then I suppose he isn't. By and by it all warms up, in its chilly way, but the solution to the mystery has a terrible "who'd-have-thought-it?" disposability, especially since the reveal oddly recalls Hergé's The Secret of the Unicorn (then again, McGregor's character does rather come across as a Tintin-style boy detective).

The favoured French line on defending Polanski has been that the US authorities should cut him some slack, for he is, after all, un grand artiste. In fact, his work for the past three decades has largely been routine, at best academic. The Ghost is one of his more accomplished recent films, but to claim that Polanski deserves concessions because he's an above-par thriller director – well, perhaps that's a less compelling argument. Still, The Ghost is intelligent, reasonably engrossing fun, and would pass the time nicely if you watched it on a plane – between Switzerland and LA, say.

Sterner stuff comes from Chinese director Lu Chuan, whose City of Life and Death is a grimly imposing evocation of the 1937 Japanese invasion of Nanjing. The same theme was explored from a European angle in the German film City of War: The Story of John Rabe, released two weeks ago, about the German official who helped shelter refugees. Lu Chuan's version, told from both Chinese and Japanese perspectives, has been a major success in China but has also got the director into deep trouble there. While painting a picture of horrific atrocities by the Japanese army, Lu tells his story partly from the point of view of a somewhat naïve Japanese sergeant (Hideo Nakaizumi). This alone has earned the director hostility, even death threats, from Chinese viewers who have objected to him humanising the invading force, but it undoubtedly gives this stark film a more nuanced dimension.

Several key figures emerge: among them, Rabe's secretary Tang (Fan Wei), foolishly confident of his family's safety; a young Chinese woman press-ganged into prostitution; and a doomed Kuomintang officer. Rabe is also prominent, but presented as ineffectual, ready to ship out when instructed by his Nazi masters. But Lu doesn't focus excessively on individuals: this is a cinema of crowds, showing how completely humanity and compassion are trampled in the movement of masses. An especially nightmarish sequence shows various styles of summary execution: different groups dispatched by bayonets, grenades, being buried alive or forced into the sea.

The film is precise in its recreation of time and place, but the severe sweep of the black-and-white photography also suggests an abstracted essence of war's horror. Unashamedly harrowing, the film doesn't need its occasional splashes of poignant orchestration to underline the emotion. Overall, this is a strikingly unsentimental and unglamorous production that looks and feels quite different from the grand-scale Chinese historical drama we're used to: a sobering reinvention of the modern war epic.

Next Week:

Jonathan Romney plays Unhappy Families, watching Greek film Dogtooth plus the latest from US suburban satirist Todd Solondz