Stephen Hawking, the famed physicist and bona fide national treasure, paused in front of a bank of photographers to pose for an affectionate portrait with his ex-wife, Jane, and two of their grown-up children, Lucy and Timothy.
They were launching The Theory Of Everything, a biographical movie charting the many ups and downs of Stephen and Jane's long marriage, which ended somewhat messily two decades ago.
The critically acclaimed film tells how the couple met and fell in love during Hawking's postgraduate career at Cambridge University before tying the knot in 1965, a couple of years after he'd been diagnosed with a rare form of Motor Neurone Disease.
It then charts, in often very moving detail, the heavy toll that the scientist's growing fame and increasingly-awful medical condition exact on their relationship.
Viewers learn how Jane was saddled with the burden of caring for a severely disabled husband while also attempting to raise three children.
Feeling lonely, unloved, and unvalued by the world's most famous living scientist, she eventually became emotionally involved with a choirmaster called Jonathan Hellyer Jones — who is now her husband.
Stephen, for his part, grew intimate with Elaine Mason, one of his nurses. He left Jane in 1990, after gaining international celebrity (and great wealth) with the success of his book A Brief History Of Time. Elaine became his second wife in 1995.
For a period, during the ensuing years, relations between Hawking, Jane, and their children were publicly strained. But after Stephen, who is now 72, divorced Elaine in 2006, things became gradually warmer.
Now, as this week's photograph suggests, the once estranged former couple are back on friendly terms.So far, so cosy. Yet away from the glitzy film premiere, not every member of the Hawking clan is entirely happy at the imminent release of the new film, which is based on Jane's 2007 memoir, Travelling To Infinity.
Indeed, I gather some important plot-lines are causing enormous distress to members of the scientist's extended family, several of whom did not consent to being portrayed in the film.
Some of his nearest relatives believe the film (which Hawking has co-operated with and has described as 'broadly true') offers a skewed and at times hurtful insight into what they consider to be private family affairs.
By way of protest, a few even went so far as to boycott Tuesday's premiere. Among them were Hawking's sisters Mary and Phillipa, who turned down invitations to attend the glamorous event after apparently taking umbrage at the way the movie portrays their late parents, Frank and Isobel.
According to a friend, the sisters believe the film misleadingly presents Stephen's mother and father as having been uncaring towards the scientist, and sometimes cruel to Jane.
'It's totally untrue, and actually a very hurtful thing to say, particularly since Isobel only died last year,' says the friend. 'What is more, several key scenes involving Stephen's parents get factual things demonstrably wrong. But viewers won't realise. So they'll all come away with a horrible impression of them.
We'll look at those scenes in detail later. In the meantime, another key figure in Hawking's life who was absent from Leicester Square was Elaine.
Now living in an £800,000 cottage in the Cotswolds, she has refrained from seeing the film, partly because she regards Jane's version of events as being 'lopsided and full of half-truths'.
'It all comes from one person's viewpoint, so people won't get a particularly rounded view of what happened,' she tells me. 'Like so many of the stories you read about Stephen, it only provides a single perspective.
'I know Mary is very upset at some of the nastiness about their parents. She has been in touch with me about it.'
Hawking's sisters are also, Elaine adds, put out by scenes in the film that give the impression they have a distant relationship with their famous brother. 'Despite what the film might suggest, Mary and Stephen are actually very, very close,' she says.
At the heart of The Theory Of Everything is a tragic (but also disputed) love story.
The film's early chapters show Jane studying literature at Cambridge (which, in fact, wasn't true), where she met Hawking at a house party.
She quickly falls for the ebullient, beer-loving, 21-year-old cosmology student, who socialises vigorously, rides bicycles dangerously, and even coxes a rowing eight. They kiss for the first time beneath fireworks at a May ball in 1963.
