Emperor Akihito's speech

Addressing a state banquet at Buckingham Palace, attended by the Queen, Duke of Edinburgh, Queen Mother and 11 other senior Royals, the Emperor said he could "never forget" the many kinds of suffering experienced by so many.

War veterans said that Emperor Akihito had not gone far enough and demanded a "real, meaningful apology."

Earlier, in a gesture of contempt, former prisoners of war turned their backs on Emperor Akihito and whistled the wartime anthem Colonel Bogey as he rode with the Queen in a Royal carriage down The Mall.

Protesters at Westminster Abbey

Later, outside nearby Westminster Abbey where the emperor laid a wreath at the Tomb of the Unknown Soldier, a memorial to the dead of World War I, around 500 protesters repeated their protest, turning their backs and humming Colonel Bogey again.

Under the post-war Japanese constitution, Emperor Akihito is a non-political figurehead and, as such, cannot formally apologise for the suffering inflicted by the Japanese imperial army.

'It truly saddens me'

But in the banquet speech on Tuesday, delivered in Japanese, he came close to saying sorry.

The Emperor said: "It truly saddens me, however, that the relationship so nurtured between our two countries should have been marred by the Second World War.

"The Empress and I can never forget the many kinds of suffering so many people have undergone because of that war.

"At the thought of the scars of war that they bear, our hearts are filled with deep sorrow and pain.

The Queen's speech welcoming the Emperor

"All through our visit here, this thought will never leave our minds. We sincerely hope that such a history will never be repeated between our two nations."

Issue will haunt Japan

"At the same time, may we express our profound respect and gratitude to those people who, despite such past sufferings, looking towards the future, have dedicated immeasurable efforts to the cause of friendship between our two countries."

But Martyn Day, solicitor for the veterans said the Emperor's remarks did not go far enough to stop the demonstrations and warned that the issue could still haunt the Japanese for many years to come.

Speaking before the speech, Mr Day conceded Emperor Akihito's expected remarks did take the situation a bit further.

"But I must say, I don't think it does anything like enough to stop the demonstrations.