John Mortimer's great achievement was to create, in Rumpole of the Bailey, a lawyer the world would love. Played by Leo McKern, the character had a Dickensian dimension, rarely attained through the medium of television. One reason for its depth was the element of truth - exaggerated for comic effect, of course - told about the loneliness of the long-winded barrister.

Rumpole perhaps reflects the barrister we want to resemble, but dread we might become. A cab on the East End rank, cunning and courageous to a fault and with an encyclopaedic recall of early 19th century English poetry, Rumpole ekes out his legal-aid living comforted by cheap red wine in a flat with Hilda his wife, “she who must be obeyed”.

Hilda's dream of becoming “Mrs Head of Chambers” is dashed in episode after episode, as Rumpole's unapologetic political incorrectness costs him any chance of promotion to silk or even appointment as a “Circus Judge”. But in full flight in the criminal courts, Horace Rumpole comes into his own as the very incarnation of English liberty.

Rumpole first appeared on television in the late Seventies when jury trials regularly featured the vaudeville routine of “police verbals” - the statements they read to juries from their notebooks, wherein hardened criminals would immediately confess on their arrest, saying “it's a fair cop, Guv”, or “you've got me banged to rights this time”. During the series, Old Bailey juries, alerted to police forensic trickery in every episode, began to throw these cases out and the buzz in the Old Bailey robing room was that Rumpole was the reason. A royal commission was established and the law was changed. Police interviews had henceforth to be tape recorded or videoed.

Times Archive, 1982: Interview: John Mortimer

'I have an obsession with the value of time. The thought of dying infuriates me'

• The curious case of John Mortimer, 1973

• The lively lives of John Mortimer, 1977

• Mortimer on Heaven and Hell, 1976

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• Sir John Mortimer

• Rumpole creator John Mortimer dies at 85

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Like many great fictional characters, Rumpole was composed from fragments of real barristers whom John admired. His blind father, of course, the irascible and poetry-quoting Clifford Mortimer, he had already immortalised in his play Voyage Around My Father.

Then, he told me, there were elements of James Burge, the flamboyant Old Bailey junior, who spoilt his chance of promotion by upsetting the legal Establishment with his defence of Stephen Ward during the Profumo scandal, and of Jeremy Hutchinson, the fearless silk with whom he occasionally co-defended. Rumpole epitomises the advocate's greatest virtue - independence and total dedication to often unprepossessing clients.

Rumpole has had an effect on the culture of the bar. When he began, the law was a more reactionary profession: those few interested in human rights were perceived as vaguely subversive. The advent of Rumpole, radical only in that he took liberty seriously at a time when the country's most senior judges were refusing to take any notice of the mounting evidence of injustice to defendants like the Birmingham Six, provoked new thinking about civil liberties. The European Court of Human Rights began at the same time regularly to find British law and its practice in breach of basic standards. Lawyers came to recognise, in Rumpole, one justification for their profession and this assisted the segue into a period where human rights are regarded as being of central importance.

The television series became an international success. After McKern's death, the role was taken by others in radio plays and each year brought a new Rumpole adventure from Penguin books. Mortimer left the Bar in the early 80s but in recent books, Rumpole has battled with ASBOs and with anti-terrorism legislation.

A few weeks ago we sat in his garden as he planned a new book in which Rumpole would deal with the Government's plans to abolish the defence of provocation and proposals to punish those who pay for sex. We don't know how Mortimer would have ended it, but knowing Rumpole, we can have a pretty good idea.

Geoffrey Robertson, QC, was John Mortimer's junior in some of his famous cases and is the author of The Justice Game (Vintage).