Tony Blair has been prime minister for nearly 10 years, and only now, as his tenure comes to an end, do we have the appearance of the first real Blair’s Britain film. By contrast, we had dozens of “Thatcher’s Britain” films before she left office, and two of them — My Beautiful Laundrette and Sammy and Rosie Get Laid — were from Stephen Frears, director of The Queen.

This new film deals with the remarkable week in British history that began on August 31, 1997, when the news of the death of Princess Diana unleashed an outpouring of unprecedented national grief. Frears and his writer, Peter Morgan (together, they did television’s The Deal), present us with the birth of the new blubbing Britain that was the making of Blair and the near death of the monarchy. It’s a docudrama based on facts — using news footage, interviews, headlines, copious research — and dramatic licence. It has the look and feel of something made for television, but what it lacks in cinematic values, it makes up for in thematic richness and dramatic power.

We are given a fascinating look into the private life behind the closed doors of Her Majesty (Helen Mirren) and Prince Philip (James Cromwell) at Balmoral — as well as those of Tony Blair (Michael Sheen) and Her Majesty (Helen McCrory) at Number 10. What we are offered is a side to the monarchy the public never sees: the emotional life that lies buried beneath that great protective fortress of protocol.

At first, HM seems a cold woman, devoid of compassion. She refuses to take part in the nation’s grief over Diana. She argues that since Diana was no longer a member of the royal family, her funeral is to be a private matter. The newly elected PM tries to become the wise adviser to the seasoned monarch; he wants her to feel the people’s pain, share their sorrow. But she will make no public comment of sympathy; there will be no lowering of the flag over Buckingham Palace, no rush to London to join the mourners. Convinced that all the “fuss” will soon die down, she is determined to stay silent in the seclusion of Balmoral.

But in Blair’s Britain, the old way of doing things — “quietly and with dignity”, as the Queen puts it — is no longer acceptable. We see the first flowers placed outside Buck House. Soon the floral trickle becomes a flood. The tide is turning against the Queen. Eventually, she is forced to abdicate not her crown, but her reticence. She gives a masterful performance of caring for the cameras.

Frears never really makes it clear what he thinks of this new blubbing Britain. But as the grief carnival grows and we watch the celebrities line up at Diana’s funeral, it’s hard not to have some sympathy with the Queen and that old Britain of the stiff upper lip. This is also a political film that makes its points quietly. It’s about how betrayal and loyalty live side by side. The hero and villain of the piece is really Blair. He is shown as the great moderniser with a mandate for change who ends up saving the monarchy when he could have destroyed it. The film pits the old Britain of reticence against the new Britain of emotional display and call-me-Tony informality. But it shows that this is nothing more than a clash of styles, not of substance.

The acting in this film is outstanding. When I first saw Sheen’s PM — he also played him in the The Deal — I thought he looked like a Blair impersonator from the Rory Bremner school of satire. But he quickly grows in authority, avoids caricature and brilliantly captures the character of the man. (Wisely, he avoids reproducing the Blair smile.) Alex Jennings looks nothing like Prince Charles, but conveys the man and the mummy’s boy perfectly. And though Cromwell lacks the accent of Prince Philip, he has his look and rudeness down pat.

As for Mirren’s performance, all the superlatives are justified. Somehow she vanishes into the character and persuades you that she is the real thing. There’s something about the set of her face — especially at “official” moments, when she stares blankly into the middle distance, the epitome of blind duty — that echoes the Queen’s while registering emotions we can all understand. Mirren has done more to humanise the Queen than even Blair did during those tearfully turbulent times.

The Queen
12A, 103 mins
Four stars