One of the first questions to spring to mind meeting comedian, TV and radio presenter, actor, adventurer, author, playwright and journalist Sandi Toksvig is whether there’s anything she’s not good at. ‘Oh, I’m rubbish at so many things – anything physical. I can’t do a forward roll,’ says Sandi. ‘I can do a Swiss roll, though, which is much better.’

It’s a characteristically modest yet hilarious statement from the Stonewall Broadcaster of the Year, who is sipping a lime and soda in the Pit bar of London’s Old Vic theatre. It’s early evening and she’s been working solidly for 12 hours – writing a magazine column at 6am, preparing a speech, then working on her play at the National Theatre studio. When we part company, she will be heading straight to the British Library to compère an awards ceremony. ‘This is a typical day for me,’ she shrugs.

Despite her self-deprecating comments, she is no stranger to feats of physical endurance. Her exploits have included canoeing the Zambezi, sailing around Britain and – as presenter of the 1980s ITV children’s show Number 73 – tackling a variety of wacky stunts. It was one such that led to Sandi’s first brush with the RNLI.

When onscreen inventor Tony English turned a ceiling tile into a hovercraft, Sandi challenged him to make something bigger that she could sit in, so he adapted a wardrobe. Her attempt to fly the resulting contraption to the Isle of Wight ended in near disaster. ‘It wasn’t his fault it blew up – it seems Victorian wardrobes aren’t as seaworthy as you might think,’ chuckles Sandi, who was fished out of the sea by a lifeboat crew. ‘I must say, though, that Tony English is a genius,’ she quickly adds, ‘and if you ever want a wardrobe hovercraft, he’s your man.

’Her quick wit and quirky humour led to more television work, including improvisational comedy series Whose line is it anyway?, team captaining on Call my bluff, and the more personal Island race. That 1995 series saw Sandi team up with friend and former Beirut hostage John McCarthy for a 3-month voyage around the coast of Britain aboard a 1911 pilot cutter. While held captive, John had dreamed of taking to the open sea but the reality wasn’t all plain sailing: ‘I really developed a sense of how dreadful the sea can be. John and I went through some pretty hair-raising conditions,’ recalls Sandi.

The two novices were nearing the end of their exhausting, eye-opening journey when they paused to draw the Lifeboat Lottery winner aboard Weymouth lifeboat. Ready to transfer back to their own craft, John and Sandi found themselves speeding in the wrong direction when a call came from the Coastguard and the lifeboat diverted to a drifting dinghy. Fortunately, it proved to be a false alarm but the experience left an impression on Sandi. ‘I thought it was breathtakingly technical. That lifeboat was an amazing piece of kit, and the professionalism of the volunteer crew really impressed me. I’ve been a big fan of the RNLI ever since.’

The thought of people volunteering to save lives at sea comes as no surprise to Sandi: ‘I’ve travelled the length and breadth of these islands and it’s a nicer, kinder, gentler race of people than you might read about in the news.’ The Danish-born 50-year-old counts the RNLI among Britain’s unique institutions but knows that the charity’s voluntary spirit is not exclusive to UK (or indeed Irish) shores. Her family moved from Denmark to the US while she was a child. ‘Every small town had a voluntary fire brigade and that’s still the case today,’ explains Sandi. ‘I think those fire crews are similar to lifeboat crews in a way – it’s giving something to your community.’ BBCA keen advocate of all forms of volunteering, Sandi makes time to support several charities despite no let up in her schedule. Tomorrow she will record travel show Excess baggage for Radio 4, do some more work on her play and spend the evening at a corporate event. At the weekend she’ll take her eldest daughter to university for the first time, before preparing to host a new series of Radio 4’s News quiz and launching her 13th book, Girls are best, a guide to women who changed the world but were overlooked by the history books.

When it comes to unwinding, Sandi still enjoys exploring the ocean, although the mysteries of the seabed intrigue her more than the mastering of sailing techniques.

‘I dive a lot. I’ve dived shipwrecks and it’s very eerie. It’s not a mythical thing – it’s a horrible reality that you wouldn’t want to be part of. So I have such respect for anyone who helps ensure they don’t happen. The idea that there are these well-trained and competent lifeboat crews out there makes me think: “Wow, how lucky for the rest of us.”’