Having taken in the thoroughness of the arrangements, I made my way into the ballroom and here the illusion was impressive. At that time it was customary for a limited number of the older generation to be invited to these gatherings. They would be drawn from the god-parents of the debutante, as well as from the relatives and close friends of her parents, and as a rule they would fringe the proceedings, chatting in some other drawing room, watching the children dancing, occasionally venturing on to the floor to demonstrate an adapted foxtrot or quickstep, before retiring fairly early for the night. They were not expected to participate as full guests since, as we all know, the sight of dancing parents is torture for the young and always was. All this was especially true of costume parties, which are rather a bore for anyone out of their thirties, and the adults would simply arrive in evening dress, occasionally with some gay little gesture, worn as a brooch or a hair ornament. None of which applied to this particular event. I do not know if it was respect for the Grand Duchess or terror (probably the latter), but every single attendee, old and young, was in costume. As a particularly witty detail, or possibly after an instruction from on high, several of the mothers and fathers had deliberately chosen outfits of a slightly earlier date than those worn by their offspring. Men in wigs and ruffles, women in high-piled, powdered hair and beauty spots, from the 1780s or ’90s, gave us all the sense that we were indeed back in the Regency and this was the older generation of the day, frowning and disapproving of modern youth. It always amuses me that this particular era, redolent as it is of Versailles and Queen Marie-Antoinette, is such a favourite costume theme with toffs. They seem to have forgotten that it did not as a whole turn out well for the privileged classes, so many of whom would leave their heads, and no doubt wigs, in the basket below the guillotine.

‘What have you come as?’ Lucy was dressed in a Jane Austen, white frock, high-waisted and pure, with a ribbon round her throat and her artificial ringlets sewn with tiny, white silk roses. She looked artful rather than innocent, but charming nonetheless.

‘I’m a hussar,’ I replied slightly indignantly, ‘I should have thought it was obvious.’

‘The trousers are wrong.’

‘Thank you for that.’ The trousers were wrong, as it happens, but the rest of the outfit was perfect, bright scarlet, heavily braided, with a fur-edged jacket slung between my left shoulder and my right armpit. I thought I looked fabulous. ‘They’re only wrong for 1815. They would be right by 1850. Anyway, it was the best I could manage. It was too late to find anything in London, so I had to raid the costume store of Windsor Rep.’

‘It looks like it.’ She stopped and stared round the room, which was beginning to fill up. ‘Where was your dinner?’

‘Chester Row. The Harington-Stanleys.’

‘Any good?’

‘Well, the food was like a shooting lunch that had been brought up to London in a rusty cake tin, but it was quite fun apart from that. What about you?’

She grimaced. ‘Mrs Vitkov. With a group to meet her daughter, Terry. At that new French place in Lower Sloane Street.’

‘The Gavroche?’

‘That’s it.’

‘Lucky you.’

She gave me what used to be called an old-fashioned look. ‘Have you met Terry Vitkov?’

‘Not yet.’

‘Don’t.’

‘Where are they from? The Balkans?’

‘Cincinnati. And believe me, Miss Terry is a piece of work.’ She stopped and nodded with a tight smile. ‘Careful. That’s her.’ I turned to look. I could see at once that we needn’t have worried and that Terry Vitkov was quite happy to be the subject of our discussion. She looked as if she were more than used to being the centre of attention. She was a good-looking girl. Indeed, she would have been very good-looking if it were not for a certain prominence of nose and chin, faintly suggesting a Man-in-the-Moon profile, which, combined with the intensity of her piercing and heavily made up eyes, gave her the air of a prisoner on the run, desperately searching the room for either an enemy or an escape route. Tonight she appeared to be dressed as a Regency courtesan, rather than a great-lady-from-times-gone-by, like every other woman there. Indeed, she was more or the less the only person in the ballroom, who would patently not have figured on the guest list of the real Duchess of Richmond. She walked up to us and we were introduced.

‘Lucy’s been telling me all the dos and don’ts for getting on in London.’ She spoke with a breathy urgency, the voice of one determined to make every human interchange register. I could see at once that despite her flashing frequent smiles, designed no doubt to suggest a spirit of girlish, flirtatious fun and displaying thereby a set of admirably white, if rather large, teeth, Terry Vitkov took herself tremendously seriously.

‘I don’t think I’ve covered them all, have I?’ said Lucy laconically.

Our companion was already training her searching gaze on the other guests. ‘Which one is Viscount Summersby?’ she asked.

Lucy checked the ballroom. ‘Over there. With the blonde girl in green, next to the big looking glass.’

Terry sought him out. Her shoulders sagged. ‘Why do they always have to look like the man from Pest Control?’ She sighed. ‘Who’s that one?’ A tall and handsome young man flashed her a smile as he passed.

‘Don’t bother. No money. No prospects.’ Lucy clearly understood her companion’s priorities. ‘Of course, he’s clever and he’s headed for the City. He may make something of himself.’

But Terry shook her head. ‘That takes twenty years and by the time they’ve got there they’re ready to trade you in for a younger model. No. I want some money from the outset.’

I nodded, sagely. ‘But not Lord Summersby.’

She smiled. ‘Not until I know I can’t get something better.’ What made this amusing, of course, was that she meant it.

We had been moving slowly in a rather sloppy presentation line and by now had nearly reached our hosts, who stood, all four together, posed against a rich curtain erected as a kind of screen for the purpose. The Grand Duke cut a melancholy figure. He was a slight and pasty-looking creature anyway, especially when placed at the side of his massive spouse and, in truth, I do not believe I ever heard him say an interesting sentence. He wore his elaborate costume, which I took to be that of the Duke of Richmond, with an air of surprise, as if he had been put into it while under sedation. Perhaps he was. His son, dressed as an officer of the guard, stared straight ahead stiffly. He could have been posing for an early daguerreotype, when you had to keep your head still for four or five minutes until it was done. His bland, mottled face exuded an air of bored and generalised geniality.

The daughter, Dagmar, technically of course the Star of the Night, looked frightened and if anything a little drab. She was a tiny creature, literally no more than five feet tall and, while one is always being told that Queen Victoria was four foot eleven and managed to run an Empire, still for most of us it is very, very small and means you spend your whole life looking up. Standing there in the shadow of her mother, to paraphrase Noël Coward, she looked like the Grand Duchess’s lunch. Dagmar wasn’t what you would call plain, even if her sallow mini-face was hard to define or at least to categorise. She wasn’t exactly pretty either, but her large eyes were arresting and she had a soft, moist, trembling mouth, usually half open and quivering and seeming to suggest she was always on the verge of tears, which, in a way, touched your heart. But she never appeared to have any idea of how to present herself. Her hair, for instance, was very dark and straight and, with imagination, it might have been effective. But it just hung there, as if it had been washed in a hurry and left to dry. I really did think something might have been made of her on the night of her own ball, but as usual nobody had tried. The dress was from the correct period but it was dull, and only faintly enlivened with a thin blue sash beneath her modest bosom. To be honest, she looked as if she had taken five minutes to get ready for a game of tennis, and so fragile that one good, strong puff of wind would carry her out of the window and down Park Lane in an instant.