The white, two-storey terraced houses, with pillared entrances, appeared even more upmarket than Mark’s impressive red-brick mansion, McNab decided. Ollie had indicated that Ms Richardson’s flat was on the first floor.

Pressing the doorbell, and not expecting an answer, McNab was surprised when he got one.

‘Yes?’ a male voice said.

‘Detective Sergeant McNab, Police Scotland, here to see Ms Richardson.’

There was a studied silence, while whoever had answered absorbed this information, then the voice said brusquely, ‘I’m afraid Ms Richardson is away on business.’

‘I’d still like to come in, sir.’ McNab’s tone didn’t brook a refusal.

‘Do you have ID?’

‘Of course.’

A moment later, the door buzzed open.

The mosaic-tiled entrance hall led to a set of stairs, at the bottom of which stood a man, who looked to be in his fifties. He wore a slightly haughty expression.

‘As I said, Ms Richardson is away on business,’ he repeated as though McNab was slightly deaf.

‘May I ask who you are, sir?’ McNab said.

‘Henry Wollstone. I live on the ground floor. Ms Richardson is the upstairs tenant.’

McNab proffered his ID. ‘Can you tell me when you last saw Ms Richardson?’

Mr Wollstone thought about that for a moment, then, shrugging his shoulders, said, ‘She’s away a lot. Maybe a week ago.’

‘Then I’d like to check Ms Richardson’s flat.’

McNab had fully expected the man to mention the Met somewhere in their conversation, but it didn’t look as though he planned to.

‘Has something happened to Olivia?’ he said instead, looking worried.

‘That’s what we’re trying to establish, sir.’

‘But why Police Scotland?’

‘Because Ms Richardson’s handbag and wallet were found in Glasgow.’

‘Glasgow! Why on earth would Olivia be in Glasgow?’ He sounded genuinely surprised.

‘That’s what I’m here to hopefully find out, sir. If you could let me check her flat now?’

McNab followed the man up the stairs, his mind already working on the fact that it appeared no one from the Met had been here. Which probably meant they already knew the fire victim wasn’t Olivia Newton Richardson and possibly had done all along.

So why had Cleverly come to Glasgow, attended the PM and demanded facial recognition software be used to identify the victim?

‘There you are.’ Mr Wollstone threw open the door, allowing McNab to enter, then attempted to follow him inside.

‘You can wait on the landing, Mr Wollstone, or I can call you when I’m ready to leave,’ McNab said firmly.

He expected a possible argument and was relieved when the man’s only reaction was a disgruntled look.

As soon as he heard footsteps descending the stairs, McNab closed the door. Despite the classical nature of the building’s exterior, in here was open-plan and modern, a sitting area with a study at one end, a kitchen at the other.