Anti-war campaigners have criticised the erection of a statue to honour World War I PM David Lloyd George.
The Parliament Square memorial unveiled by the Prince of Wales and Duchess of Cornwall is the first to the "Welsh wizard" on the streets of London.
A letter to the Daily Telegraph signed by playwright Harold Pinter and others claimed he left a legacy of violence.
But historian Kenneth O Morgan called Lloyd George a great radical and a democrat who deserved to be honoured.
Other signatories include the Nobel Prize-winning playwright Harold Pinter and campaigning journalist John Pilger, and former United Nations humanitarian co-ordinator in Iraq, Denis Halliday.
They said Lloyd George's leadership saw bombing by British war planes across the Middle East, and left a legacy in the current violence in Iraq.
They wrote: "All of which makes today's celebration of Lloyd George's legacy highly topical and disgraceful."
But Lord Morgan said: "The bombing of Iraq was part of his government, but so too was the attempt to remake the world after 1919.
"And Lloyd George was the first man to try and bring the new Soviet Union into the commity of nations.
"This new statue honours... a courageous young opponent of 'methods of barbarism' in the South African war, much cited during the invasion of Iraq and its grisly aftermath."
Prince Charles unveiled the statue as Prime Minister Gordon Brown and two former premiers - Baroness Thatcher and Sir John Major - looked on.
Charles praised Liberal Lloyd George as he unveiled the 8ft (2.4m) bronze artwork. There is another statue of Lloyd George in the House of Commons.
The prince told invited guests, who included many descendants of the statesman: "I feel it's wholly appropriate that David Lloyd George should be commemorated this way in Parliament Square.
"In the course of a decade, beginning approximately a century ago, he established himself as one of the greatest social reformers and war leaders of the 20th Century."
Charles, who is a royal patron of the appeal trust that raised £350,000 to have the statue created, added: "Though he never forgot his Welsh roots, it is as a national and international statesman that he will best be remembered."
Lloyd George was MP for Caernarfon and prime minister from 1916 - 1922.
He is seen as playing a vital role in Britain's victory in World War I and in the subsequent Versailles peace negotiations.
He had earlier been chancellor of the exchequer and was largely responsible for the introduction of old age pensions, unemployment benefit and state financial support for the sick and infirm.