Obituary: Lord Janner of Braunstone

As the more overbearing Barnett had done, he, too, defended the state of Israel and vocally attacked antisemitism. He investigated war crimes and was a powerful and implacable supporter of the campaign for Soviet Jewry. It was during this campaign that he expressed his fury at an invitation to London by the Labour government and the TUC to former Kremlin head, Alexander Shelepin and the Soviet zealot Boris Ponomarev. An angry demonstration forced the cancellation of the trip and he and Ponomarev exchanged fire when Janner offered him a copy of Magna Carta.

Janner was a key proponent of an annual day of remembrance in January for genocide victims in Britain. He also promoted legislation enabling Britain to prosecute war criminals where crimes were committed outside British jurisdiction. He campaigned, too, for safety at work and was in every way a genuine exponent of the socialist principles he espoused. Lord Janner's erudition was widely praised; he was a gifted linguist, said to speak nine languages, wrote several books, and his interests even extended to membership of the Magic Circle - a whimsical reflection, perhaps, of his mercurial nature.

All the more tragic then that his unswerving battle for social justice, all characteristics of a man of principle, should now be overshadowed by a torrent of child abuse allegations under an intense media spotlight - none of which is now likely to be resolved in the courts. As Lord Janner became engulfed in the fog of dementia, he was deemed unfit to plead, but the clamour for justice on behalf of his alleged victims only grew louder.

The first murmurings of allegations that he was a serial abuser of young boys were heard in 1991, but were not investigated until recent months. Janner and his family consistently denied them. It took 20 years before fresh allegations by more than 20 men were made against Janner, followed by a nine-month investigation by Leicestershire Police.

Lord Janner inherited his father's Braunstone constituency in Leicestershire, which both had held successively for more than 50 years. The anecdote goes that he accepted the Labour constituency on a whim because, at the age of 77, Barnett suddenly withdrew his candidature for the 1970 election while the Vote Janner posters were fresh off the press. To save printing costs Barnett proposed Greville instead! He went on to hold Leicester West for 27 years. Both he and Barnett were ennobled, Greville by Tony Blair.

A leading and vigorous member of the Jewish community, Greville Janner's involvement with Jewish causes and organisations was wide-ranging and international. Following in the towering footsteps of the father he often felt dwarfed him, he became president of the Board of Deputies from 1979 to 1985, headed the World Jewish Congress, the Inter-Parliamentary Council Against Anti-Semitism, the Commonwealth Jewish Council, the National Council for Soviet Jewry, the Holocaust Educational Trust, the British-Israel parliamentary group, the all-party Group for Jews in Eastern Europe and the all party War Crimes Group.

He considered the War Crimes Act his greatest achievement. It was launched by Margaret Thatcher under his pressure, but was rejected by the House of Lords, finally passing into law in 1991. In the immediate post-war period, Janner had been a war crimes investigator with the Royal Artillery in Germany and it sparked his lifelong campaign to bring all Nazis to justice.

Yet his interests extended to the homeless, in whose name he founded an all-party committee and chaired another on industrial safety for 24 years.

He was responsible for a review into the rights of au pairs to be male and managed to stop German veterans from marching through London on the 50th anniversary of VE-Day.

His mother Elsie Cohen CBE chaired the Juvenile Courts Panel and was life president of the Central Council for Jewish Religious Education. Fearing a Nazi invasion, his parents sent him to Canada, where he studied at Bishop's College School in Quebec and subsequently won a scholarship to St Paul's.

After National Service, he took up an exhibition to Trinity Hall, Cambridge and chaired the University Labour Club, becoming president of the Union in 1952. Dapper and athletic in build, he was a noted sprinter and became president of his college athletic club.

The next step was Harvard Law School where he was a Fulbright scholar and became international secretary of the National Association of Labour Students. A Harmsworth scholar at the Middle Temple, Janner was called to the Bar in 1955 where he launched a criminal practice defending members of the Direct Action Committee Against Nuclear War, following sit-down strikes. Later he specialised in employment and consumer law, taking silk in 1971.

He entered the Commons in 1970 and in the February 1974 election he took the new constituency of Leicester West by a mere 1,712 votes.

As both a hard-working MP and QC, he also created a successful business from his knowledge of employment and consumer law, running law courses for businessmen and producing more than 50 popular handbooks on related themes.

But Janner was also a controversial figure who once famously stormed Radio Leicester demanding to be interviewed.

On a more serious level, Janner's internationalism became evident when, as president of the Board of Deputies, he was permitted by the then President Sadat of Egypt to remove a 9th-century Torah from a Cairo Synagogue for restoration purposes. In 1981 he became embroiled in the fate of Swedish diplomat Raoul Wallenberg who saved thousands of Hungarian Jews before disappearing into the Gulag. Janner chaired a Stockholm hearing on his fate which pressured Russia to produce Wallenberg or prove its claim that he died in prison in 1947.

Janner was nothing if not persistent. In the early 1980s, news broke that Kurt Waldheim, Austria's president had been an SS officer in wartime Yugoslavia. While his efforts to indict the former UN General Secretary proved baseless, Janner's investigations identified several war criminals in the United Kingdom.

He once said he was "driven by vengeance over what had happened to my Jewish people" and regarded himself as a disciple of the Nazi-hunter Simon Wiesenthal.

Greville Janner married Myra Sheink, Australian niece of former Chief Rabbi Dr Israel Brodie in 1955, and they had a son and two daughters. He was said to have been devastated by her death in 1996. He left the Commons with a life peerage a year later.

In 2009, Janner was diagnosed with Alzheimer's disease. And by 2015 he required round-the-clock care for his dementia. The family can only hope that Greville Janner's spectacular fall from grace will not completely eradicate his many achievements for decades to come.

Lord Janner is survived by his son, Daniel, a QC briefly a Labour candidate and now a Conservative; Marion Janner, chief executive of the social justice charity Bright, which runs the Star Wards project, awarded an OBE for services to mental health in 2010; and Laura Janner-Klausner, National Movement rabbi for the Movement for Reform Judaism.