Prime Minister Tony Blair spoke yesterday of the Queen Mother's "total and selfless" devotion to duty as preparations intensified for her Lying in State and funeral.

Mr Blair made his moving tribute during a special session of the Commons, recalled from its Easter recess.

Parliament observed a one-minute silence and Mr Blair spoke of how the Queen Mother spanned the generations and a vast sweep of history.

Meanwhile, it emerged that her four grandsons will mount a vigil at her coffin as she lies in state in a gesture reminiscent of the tribute paid to George V in 1936 by his sons.

The Duke of York told of the plan as he paid his respects at his grandmother's coffin, now resting in the Queen's Chapel at St James' Palace in London.

The vigil by the Duke of York, the Prince of Wales, Viscount Linley and the Earl of Wessex, with the four Royals standing guard at each corner of the coffin, is expected to take place on Monday.

The poignant ceremony will be reminiscent of the vigil mounted for George V in 1936, on the same spot in Westminster Hall, when his sons, Edward, Albert, Henry and George, stood solemnly at the late king's coffin.

Mr Blair told a hushed Commons her combination of high integrity and simple humanity had made the Queen Mother not just respected but loved. "She loved her country and in turn her country loved her," he said.

MPs and peers, in sombre mood and dressed in black, packed the chambers to pay their own tributes and to take part in the period of mourning leading up to the Lying in State in Westminster Hall from Friday and her funeral on Tuesday.