Gladstone was a man of cast iron convictions, but as Jenkins shows in page after page of this masterful biography, the convictions he held today were propounded with all the skill, vehemence and holy certainty of the entirely opposing convictions he held yesterday.

The rock solid image Gladstone gained in his later career has obscured the reality of what an impetuous and even reckless man he always was. Gladstone twice even tried to escape from his parliamentary career: once when he became the Corfu-based Commissioner for the Ionian Islands in 1858 and in 1844 when he wrote to the prime minister proposing he should resign his cabinet seat and become special envoy to the Vatican. Sir Robert Peel wisely ignored the letter.

“Gladstone was not a dreadful person,” Jenkins tells us, contradicting Clement Attlee who said the opposite. Jenkins needs to reassure us of this because almost everything he tells us about the great man, particularly in his early chapters, inclines us to the opposite view. Most obviously this appears in Gladstone’s sickening religiosity, which he spread over everything to the extent of saying the l832 Reform Bill had “something of the Anti-Christ” about it, and later planning to appoint only churchgoing Anglicans to public service jobs, however humble.

“Sin, condemnation and fear played a great part in his religion,” writes Jenkins. This is not only manifest in his miserable shame at masturbation and the use of pornography, but in what is Roy Jenkins’ claim to have contributed to Gladstonia: compiling the accounts of the Grand Old Man’s relationships with prostitutes.

Gladstone was an unhappy, tormented man, never at ease with himself, who found it easier to converse with streetwalkers than with women of his own class. He discovered this early: his first recorded encounter with a prostitute was at the age of 18 when he went to Oxford on a preliminary visit before joining the university. If this was a chance meeting, he took advantage of it, as he saw her again the following day.

In middle and old age he would be seeking out the same prostitutes again and again, sometimes going to their lodgings to look for them. He was obsessed with one called Elizabeth Collins, for example, in the summer of l851 when he was 41, and once recorded spending two hours in her rooms, “a strange and humbling experience”, after which he went home to scourge himself.

If his intention was genuinely the reclaiming of these women’s souls, he should long since have given it up as a bad job: he recorded in 1854 that of the 80 to 90 prostitutes he had dealt with in the previous five years, only one had given up her life of sin. His joy in the presence of his favourite prostitutes is undisguised, and his protestations that he had never practised “infidelity to the marriage bed” imply, by their very specific nature, that he had done other things which fell short of it.

Jenkins sees Gladstone as “in many ways the greatest figure of the 19th Century” and finds his failings easy to excuse. These locker-room comparisons of who was the greatest figure or greatest prime minister do not impress. Gladstone was a poor prime minister where foreign affairs were concerned; no more than average as a party leader; an exceptionally good chancellor of the Exchequer; and a brilliant performer in the House of Commons and on the public platform. It is as a peacetime prime minister dealing with domestic policy that his reputation must primarily be assessed.

Jenkins moves through the complex political history of the 19th Century with skill, often in more detail than is strictly necessary, but no one is obliged to read every word about the household franchise or the Maynooth grant. Jenkins aimed at writing a comprehensive biography which would be the standard work for many years, and he has achieved this.

Apart from the sexual material, Jenkins has no new historical insight, which is unremarkable considering the amount already written about Gladstone. More surprising is the lack of any additional insight provided by Jenkins’ own considerable political career, which included splitting his own party, which he has in common with Gladstone. Were there doubts or fears? Did he ever countenance the slightest thought that he had made a dreadful mistake?

Gladstone was indeed great, though his greatness was very sporadic. Jenkins is clearly a fan, but, despite his enthusiasm and Gladstone’s late radicalism, which endears him to the hearts of modern liberals, my increasing impression in reading this long life was what a truly impressive statesman was Disraeli.

Jad Adams is the author of Tony Benn: a biography (MacmillanPan).