Anthony Carrington is a long-standing friend of her father, although it has been many years since Harriet saw him. She had been a child when they had last visited his shop together and her father had bought her a small silver locket to wear at a party. She had been, what, twelve? She had felt very grown up at the time. It was so long ago.

Mr Carrington had been puzzled by Miss Littlemore’s visit to his shop on Monday afternoon. Something had not been quite right. He really could not believe it had been Gerald Littlemore’s daughter, although it had been years since he had seen her. There had been something affected in her manner. And then, recalling the theft at Enderby’s in Kensington, he had decided to call Scotland Yard. Arthur MacKenzie had listened very carefully as the jeweller had voiced his suspicions.

‘It wasn’t Harriet,’ the inspector says now. ‘That is my point.’

‘It’s not even your birthday.’ Gerald carries on, ignoring him. ‘Your birthday is November, not March.’

‘He might have been confused,’ Isabel says, handing a small slice of cake to MacKenzie. ‘He is getting quite old.’

‘He’s not that much older than I am,’ Gerald huffs.

‘A young woman, short hair’ – MacKenzie looks at Harriet – ‘in a smart beige coat and wearing a string of pearls. She said that her name was Harriet Littlemore, but it was not Harriet. She was dark-haired, for a start.’

Harriet reaches a hand to the pearls at her throat. Dark hair, calling herself Harriet.

‘Well, I have not set foot in Mr Carrington’s shop since I was a child, I can assure you. I have no idea who it might have been. I cannot help you, I’m afraid.’ She gives MacKenzie a polite smile.

‘One of the thieves you seem so enthralled by?’ he responds, still staring pointedly at her. ‘Ruby Mills, perhaps? I can spare a man to watch the shop, I suppose. Keep an eye on the place in case she returns.’

‘Ruby Mills?’ Isabel holds the cake knife in mid-air. ‘That dreadful creature you wrote about, Harriet? I told you she would come to no good. And if she’s making use of your good name – our good name – then that really is the limit.’ She cuts firmly into the fruitcake. ‘You should never have had anything to do with her.’

‘I’ve not had anything to do with her,’ Harriet lies, taking the proffered cake. ‘Except to write about her.’

‘Carrington said she had excellent taste,’ MacKenzie says. ‘Found the best quality diamonds like an expert.’

Harriet hides her smile by biting into the cake.

‘I don’t want Harriet’s name mentioned, Arthur,’ Gerald says. ‘When you catch this girl, I mean. It wouldn’t do for her to be associated in any way with a criminal like that.’

‘Of course not.’