Prepared as he worked on a BBC television series to mark the anniversary of her accession on February 6, 1952, it is well written, informative and, thankfully, avoids undue deference.

Marr, a respected Scottish journalist-turned-broadcaster, is a converted republican. 'Honestly, the more you see of her in action, the more impressed you are,' he writes. 'She has been dutiful, but she has been a lot more than dutiful. She has been shrewd, kind and wise. Britain without her would have been a greyer, shriller, more meagre place.'

Of course, fate often nearly intervened to stop her reaching the throne, Marr writes. First Eddy, Duke of Clarence, the 'weak, rackety elder brother' of George V, died of flu in 1892, leaving the way clear for the man Princess Elizabeth came to know as 'Grandpa England'.

Next, briefly, was Edward VIII, the queen's fun-loving 'Uncle David', a 'vain, self-indulgent celebrity ... the Bad King, the Windsor Who Got It Wrong', who turned his back on the monarchy to let the queen's stuttering father, Bertie, George VI, take over.

But even then, 'some men of authority in the state' seriously considered bypassing Bertie during the 1936 abdication crisis and settling the crown on his youngest brother, the more dashing and outgoing Duke of Kent. 'Had that happened, there would have been no Diamond Queen for the British to celebrate in 2012,' says Marr.

An admiring Marr focuses on the difficulties in her reign, her relationships with her prime ministers, and her solid efforts to strengthen the shaky foundations of the Windsors during her reign. But he is not so admiring of her son and heir, Prince Charles, who is 'not big on self-abnegation'.

The book is never too dry and serves up interesting images of the queen taking breakfast of toast and Earl Grey tea while 'enjoying the music (ignorant people would call it noise) of her personal bagpiper in the garden'.

Marr also provides one or two amusing stories. One features Princess Victoria, the sister of George V, who rang him at Buckingham Palace and began the conversation, 'Hello, you old fool', only to be told by the operator: 'Beg pardon, your Royal Highness, His Majesty is not yet on the line.'

Another recalls ballet choreographer Sir Frederick Ashton, a favourite dance partner of the queen mother, who is about to take her hand only for the queen herself to suggest he dance with her. 'You cannot refuse your monarch.' As they twirled round, passing the queen mother's table, she hissed at Ashton, 'Social climber',' Marr writes.

The queen shows no sign of stopping, but Marr will miss her passing. 'For most of us the Queen seems always to have been there ... along with the seasons and the weather. One day, of course, she won't be there. Then there will be a gaping, queen-sized hole in the middle of British life.'