When Margot Asquith’s name crops up these days, it is usually in a retelling of the story about her meeting Jean Harlow, sexy star of the silver screen, who repeatedly called her Margotte. Eventually, Margot became irritated. ‘No, my dear,’ she corrected. ‘The “t” is silent, as in Harlow.’ It’s a good story, but apocryphal and, I was always told by those who knew her (she was my great-grandfather’s second wife), quite untypical of her. No matter. She had plenty of good lines that were unquestionably her own, as this diary vividly attests.

She was at her best when analysing friends and enemies, which were sometimes interchangeable categories. And as the Prime Minister’s wife during the period covered by this volume, she occupied a good vantage point from which to draw her portraits. The dramatis personae of the diary are worthy of one of Shakespeare’s histories, including as they do practically all the prominent British politicians of the Great War. They also include her husband’s five gifted children by his first wife, many friends he acquired in a career of academic as well as political success, and the members of Margot’s own circle. Some of these were drawn from the new-rich Tennant family into which she was born, others from the Souls, a social set centred on the memory of her sister Laura, who had died after childbirth. Among its members were Conservative politicians such as Arthur Balfour and George Curzon and a score of clever, artistic women whose somewhat pretentious explorations of the soul were leavened by bicycling and charades.

Margot was fast, both on the hunting field and, some said, off it. She was also quick of mind, though uneducated. She was candid to a fault, extravagant, astringent, egotistical and tactless. She was also brave and supremely loyal, most notably to her husband, whom she chose to call Henry, though almost all others called him by his first name, Herbert. In personality she was utterly unlike him, and her trenchant views, usually formed not so much on the merits of the issues as on the politicians who supported or opposed them, often made her a liability.

Yet she was never dull, and often perceptive. Almost every page of her diary carries an interesting remark. Of Kitchener she says, ‘I am amazed often at his ignorance, but… he is teachable, not obstinate, and very clever… He gets on well with H[enry], who likes him and finds him quick, which with Henry is everything. K never bores.’ Bonar Law, the leader of the Unionists, ‘is cunning, cautious and shallow… A feeling of half-mourning clings to his personality. He invests everything with dullness.’ (She badly underestimated ‘this 5th rate man’.) Edward VII’s mistress Alice Keppel, ‘the last declared lady of any King’, is ‘coarse, kind, truthful and gay’. Though she was devoted to Sir Edward Grey, the foreign secretary, she found him ‘far too set and old… I long for a little red blood in his veins and this sometimes gets the better of me. I like crimson blood.’

Churchill makes frequent appearances. On his 40th birthday, 1 December 1914, she asks, ‘What is it that gives Winston his pre-eminence? It certainly is not his mind… Winston has a noisy mind. Certainly not his judgment: he is constantly very wrong indeed… It is of course his courage and colour… He is at his very best just now: when others are shrivelled with Grief… Winston is intrepid, valorous… longing to be in the trenches… happy even… he is a born soldier.’ This judgment is confirmed six months later when Churchill unguardedly tells her, ‘I would not be out of this glorious, delicious war for anything the world could give me,’ before adding, ‘I say, don’t repeat that I said the word “delicious” — you know what I mean.’ But a fortnight later she remarks, ‘Well, I like Winston much better than I did. What I mind is his incapacity to grow up. I feel it about so many people… born clever or geniuses, like Harcourt, Rosebery or many others, but the same in the nursery, the school-room, the cabinet.’ And by August 1916 she is castigating him for caring ‘more for one’s self than for any other creature’. ‘I would be sorry for Winston but he fills me with contempt… he was au fond always a bore & diseased by blighting Egotism.’

Long before this the Shakespearean history has become a tragedy. The war, which in the average opinion of ‘everyone at dinner’ (presumably in 10 Downing Street) on 24 July 1914 was expected to last ‘3 weeks to 3 months’, had become a hideous nightmare. The Prime Minister, praised on all sides at the outset of the fighting and unrivalled in his mastery of the House of Commons, was now seen as remote, indolent and incapable of bringing about the changes needed to achieve victory. He had lost most of his support in Parliament and even among Liberals in the country at large; he, and Margot, had lost much of their popularity.

The way was opening for David Lloyd George, now secretary of state for war, to become prime minister a few months later. Margot, who has admitted her susceptibility to his charm, good looks and vitality, still believes he cannot succeed: ‘He moves rapidly from failure to failure, turning friends into Foes as a man might turn pictures to walls… All he undertakes drops in chaos and confusion on a floor littered with covered tracks.’ But she underrates both the seriousness of her husband’s position and the feeling that Lloyd George can do better. The end is nigh for Asquith’s administration, and with it his political career.

The strength of Margot’s diary lies in her closeness to the centre of events and the vigour with which she records them. Not surprisingly, she chooses to overlook some. Her husband’s dependence on drink is not mentioned. Nor is his dependence on Venetia Stanley, to whom he was constantly writing letters (occasionally during official meetings, even one discussing the disastrous Dardanelles expedition), though her name crops up quite often. Fortunately, the omissions are admirably made good in the introduction by the late Michael Brock (he died in April) and in the footnotes written by him and his wife, Eleanor. Indeed, the introduction is a model of its kind, setting people and events in context in masterly fashion — and, in case you’re wondering, the love affair with Venetia was, in Mr Brock’s view, courtly, not carnal.