For a man at the centre of a storm that has rocked the political establishment, Peter Mandelson has spent the week looking remarkably relaxed. Day after day, as MPs have grilled civil servants over who knew what when about the former US ambassador’s security vetting, and police continue to investigate serious allegations over his own conduct, Mandelson has stepped out of his Regent’s Park mansion and pottered across the road to take his dog for a walk.

Smart-casually dressed in jeans and a jumper and holding in front of him a plastic ball-thrower, he has set off for the park like a weekending solicitor on his way to an egg and spoon race. There have been occasional small smiles for the photographers at his gate, but no comment. The message appears to be: I am insouciant, normal. Not in prison.

Dogs need to be walked, and Jock, Mandelson’s 10-year-old brown and white border collie, is no exception. But the former ambassador could easily have chosen to stay with a friend, or hopped in his car to walk the dog in a different park, or done a Fergie and gone to ground entirely. But “Mandelson’s past record is not to hide away after big setbacks,” says his biographer, Donald Macintyre. “I think his temperament is, ‘I’m bloody well gonna go out there and show them I’m still alive.’ And so here he is, at his highly conspicuous central London pile, in easy reach of every photo agency in the capital.”

As the man often described as a master of political spin knows well, while you may have nothing to say on the record, the post-disgrace doorstep photo says plenty all by itself. Should you find yourself with a scrum of photographers at your door, you can slump down in your seat in the hope they can’t see you, like Andrew Mountbatten-Windsor; engage your wife in an overenthusiastic snog to attest to the health of your marriage, like Dominic West; or walk off with a paper bag over your head, like Shia LaBeouf. But whatever you do – even hiding inside with the curtains drawn – will be judged.

“The doorstep photo has become a strange modern ritual when someone’s life is falling apart,” says Lauren Beeching, a PR adviser who specialises in crisis management. “It becomes a test and the public is marking it, whether they realise it or not. Walk too fast, you look guilty; walk too slowly, you look arrogant; smile, you don’t care; don’t smile, you’re broken. There’s almost no version of leaving your own front door that the public won’t read something into.”

Walking your dog, in this context, can be a tight-lipped skulk behind dark glasses, as when the sacked Radio 2 DJ Scott Mills was recently spotted “looking downcast” with his husband and cavapoo. Or, it can illustrate your defiant nonchalance, as Roy Keane seemed eager to convey with his daily walks with his labrador Triggs after being sent home from the World Cup in 2002.

Emerging in your running gear, similarly, can be viewed less as a burst of activity and more an attempt to run away from accountability, as David Cameron and Matt Hancock have discovered.

For a rash of Tory politicians caught with their pants down in the 90s, a doorstep press scrum often meant a posed photograph alongside their grimly smiling wife and children – the heritage secretary David Mellor even persuaded his inlaws to join in after his relationship with Antonia de Sancha was exposed in 1992. His marriage ended shortly afterwards.

More recently, the actor Dominic West, after being photographed kissing a co-star, posed for doorstep photos kissing his wife, Catherine, before (unconventionally) handing out a note reading: “Our marriage is strong and we are very much still together”. If you say so. Some observers were focused on the balled-up tissue in her right hand while her left, with ring finger, stayed firmly in her pocket.

Doorstep appearances may be used as attempts to charm and disarm – like Boris Johnson offering cups of tea to reporters more interested in asking him questions. Or they can convey contempt – Vogue suggested that Dominic Cummings’s fashion choices when facing paparazzi outside his home created the impression “he’d been doing acid with shepherds”, describing them as “a masterclass in eff-off dressing”.

In Mandelson’s case, the thinking behind his appearances may be very strategic, argues Andrew Chadwick, a professor of political communication at Loughborough University. “The first thing that came to mind for me was, ‘flood the channel’,” he says, meaning provide lots of new, sunny action shots and squeeze out less flattering recent photos. “He knows that journalists need images, and he knows how to convey that sense of defiance, freedom, ‘there’s nothing going on here’.”