For One Knight Only: Judi Dench, Maggie Smith, Derek Jacobi and Ian McKellen prove a delight

It's the simplest of ideas. Gather together four of our most distinguished thespians (two dames and two knights) on Zoom, get another venerable but slightly younger theatrical knight to ask them some questions, then invite an audience of 7000 from around the world to listen in to the conversation.

The resulting encounter between Kenneth Branagh as question master and Judi Dench, Maggie Smith, Derek Jacobi and Ian McKellen raised £300,000 for the theatrical charity Acting for Others, which provides emotional and financial support to theatre workers in times of need. That was the main business of the night.

But the actual event, which stretched over 90-minutes, was a delight in itself, an intimate encounter that felt like one of those dream dinner party games where you get to invite your fantasy guests. That sense of casual nearness, of inviting these people into your home, was emphasised by the fact that they were talking from their own living rooms via a slightly ramshackle Zoom link.

The questions, sent by the audience, ranged from the historical (what was the first thing they themselves saw on stage? Who were their inspirations?) to the descriptive (who would they most have liked to act with? Had they ever stolen a prop from a set?) to the frankly bizarre (tell us a Christmas cracker joke! What's your favourite sandwich?). Branagh proved a genial host, gently coaxing reminiscences from people he clearly knows well and who treat him like a favoured nephew.

The depth of their experience and the warmth of the chat made it riveting. I loved McKellen's story of Patrick Stewart seeing a ghost on stage, and Maggie Smith's memory of losing a skirt, when she put her heel through the hem. Dench recalled that she once returned from the long-break in the middles of The Winter's Tale without having put a skirt on at all. Jacobi's account of wounding Peter O'Toole in a sword fight was both fascinating and beautifully told; Branagh came up with Dench's best piece of advice to him: "Stop flailing your arms around like a f***ing windmill!" Her own memory of her first acting performance as a snail was a hoot.

There was a thoughtfulness to the entire event, which took it gently beyond the practised polish of your normal onstage Q and A. At one moment, McKellen and Jacobi discussed whether performing had made them more understanding of people who do evil things, and whether Hitler (whom Jacobi once played) had to be excluded from that. At another, Smith's reaction to the idea that she could ever have been anything other than an actor – "I'd be a blank…I just can't imagine it" – told you everything you could ever wish to know about the dedicated perfectionism that has driven her on.

When the four of them brought the evening to a close by sharing Marcellus's speech from Hamlet about the Christmas season, with Dench accorded the dying fall of the closing "So hallow'd and so gracious is the time" it was similarly a glimpse of the understanding and the passion that has guided their great careers – and made the hours in their company so well spent.