Daisy took off her dress and put on the shirt. Ruby helped her with the unfamiliar studs and cufflinks. Then she climbed into Bing Westhampton’s trousers, black with a satin stripe. She tucked her slip in and pulled the suspenders over her shoulders. She felt a bit daring as she buttoned the fly.

None of the girls knew how to knot a tie, so the results were distinctly limp. But Daisy came up with the winning touch. Using an eyebrow pencil, she gave herself a moustache. ‘It’s marvellous!’ said Eva. ‘You look even prettier!’ Daisy drew side-whiskers on Eva’s cheeks.

The five girls met up in the twins’ bedroom. Daisy walked in with a mannish swagger that made the others giggle hysterically.

May voiced the concern that remained in the back of Daisy’s mind. ‘I hope we’re not going to get into trouble over this.’

Lindy said: ‘Oh, who cares if we do?’

Daisy decided to forget her misgivings and enjoy herself, and she led the way down to the drawing room.

They were the first to arrive, and the room was empty. Repeating something she had heard Boy Fitzherbert say to the butler, Daisy put on a man’s voice and drawled: ‘Pour me a whisky, Grimshaw, there’s a good chap – this champagne tastes like piss.’ The others squealed with shocked laughter.

Bing and Fitz came in together. Bing in his white waistcoat made Daisy think of a pied wagtail, a cheeky black-and-white bird. Fitz was a good-looking middle-aged man, his dark hair touched with grey. As a result of war wounds he walked with a slight limp, and one eyelid drooped; but this evidence of his courage in battle only made him more dashing.

Fitz saw the girls, looked twice, and said: ‘Good God!’ His tone was sternly disapproving.

Daisy suffered a moment of sheer panic. Had she spoiled everything? The English could be frightfully straight-laced, everyone knew that. Would she be asked to leave the house? How terrible that would be. Dot Renshaw and Nora Farquharson would crow if she went home in disgrace. She would rather die.

But Bing burst out laughing. ‘I say, that’s terribly good,’ he said. ‘Look at this, Grimshaw.’

The elderly butler, coming in with a bottle of champagne in a silver ice bucket, observed them bleakly. In a tone of withering insincerity he said: ‘Most amusing, Sir Bartholomew.’

Bing continued to regard them all with a delight mingled with lasciviousness, and Daisy realized – too late – that dressing like the opposite sex might misleadingly suggest, to some men, a degree of sexual freedom and a willingness to experiment – a suggestion that could obviously lead to trouble.

As the party assembled for dinner, most of the other guests followed the lead of their host in treating the girls’ prank as an amusing piece of tomfoolery, though Daisy could tell that they were not all equally charmed. Daisy’s mother went pale with fright when she saw them, and sat down quickly as if she felt shaky. Princess Bea, a heavily corseted woman in her forties who might once have been pretty, wrinkled her powdered brow in a censorious frown. But Lady Westhampton was a jolly woman who reacted to life, as to her wayward husband, with a tolerant smile: she laughed heartily and congratulated Daisy on her moustache.