Precipice by Robert Harris review – the prime minister’s affair

Robert Harris has a knack for lighting on a fascinating episode of history – in his 16th novel, the affair between then prime minister Herbert Henry Asquith and the “lithe, vivacious” aristocrat Venetia Stanley during the lead-up to the first world war – and creating from it a tight and satisfying plot.

Precipice interweaves the perspectives of 61-year-old Asquith and 26-year-old Stanley with that of Special Constable Paul Deemer, who is investigating the origin of highly classified telegrams that turn up scattered across the countryside over the summer of 1914. It turns out that Asquith himself has been tossing them from his car window to impress Stanley, and soon Deemer is intercepting the lovers’ post to discover a gobsmacking array of “decrypted telegrams, secret information, such a plethora of extravagant declarations of love!”

This casual disregard for (inter)national security is astonishing but true, and it’s great material for fiction. Precipice is meticulously detailed, studded with juicy trivia of the sort readers can’t help but announce to the room: did you know, for example, that in Edwardian London the post went 12 times a day? The behind-the-scenes government business of Britain’s entry into the war is engaging, with enjoyable guest appearances from Churchill and Lloyd George, plus a cast of society nicknames – “Bongie”, “Puffin”, “Goonie”, “The Cossack”. The selfish, careless life of the Edwardian elite is intelligently observed.

Asquith wrote about 300,000 words to Stanley during their relationship, and Harris quotes extensively from these letters, a risky move since it invites comparison between the real voices of individuals and their fictional rendering. Harris is reliably attentive to tone and vocabulary: the voice of the novel feels all-of-a-piece. Disappointingly, the content doesn’t quite match.

Asquith and Stanley are surprisingly staid and steady; expressions of passion and yearning are restricted to their real letters. As Deemer puts it, “to share so many state secrets with a young woman less than half his age, to send them through the ordinary post, and to show her decrypted telegrams – that was beyond love, surely? That was a kind of madness.” Indeed, and the precise nature of Asquith’s madness is the central question of this novel. A shame, then, that Harris is unwilling to answer it.

Was Asquith hopelessly infatuated? A narcissist seeking adulation at any cost? Readers of Precipice will never know. Stanley’s letters don’t survive (Asquith was just sane enough to destroy them, whereas she, perhaps equally sanely, squirreled his away), so it’s difficult to gauge what she got from it. A rush? Validation? Leverage? “I feel it’s almost my patriotic duty to keep him happy,” she says, which rings true; Deemer finds “something tragic” about Asquith, but then his function is to provide an outsider’s commentary on the letters, rather than drawing his conclusions from the prime minister as he appears on the page.

Harris’s Acknowledgment notes that “it strains credulity that the affair was not, at least in some sense, physical” – but his fiction only coyly implies this via blinds being drawn and coats spread out. No need for bodice-ripping, but it’s once more frustrating that the obsession at the core of Precipice is circled but never approached. Harris prefers the safety of trivia, offering in the same tone as he discusses the postal service that “frottage was the commonest form of pleasure”. Simultaneously too much information and perfectly unilluminating. Perhaps this sums up the problem: as a corridors-of-power adventure, Precipice is well researched and expertly constructed, but it shies away from psychological insight into these two forceful individuals – and seems to prefer it that way.

• Precipice by Robert Harris is published by Hutchinson Heinemann (£22). To support the Guardian and the Observer, order your copy at guardianbookshop.com. Delivery charges may apply.