Brian Blessed has already sung me his rendition of Nessun Dorma, talked enthusiastically about dinosaurs and space travel and tried to convince me that yetis exist, all on full volume and so excitedly he’s tripping over his words.
There's a distinct sense that I'm talking with an overimaginative child on a sugar rush if it weren’t for that trademark booming, operatic voice.
In fact the larger-than-life actor has just turned 86, but he doesn't mind if I find that hard to believe… because so does he.
"I'm a child, I'll never grow up, I'm Peter Pan," bellows Brian, as if projecting his voice on a West End stage. "I feel exactly now as I felt when I was five years of age.
"I'm sick to bloody death of people who make a pact with old age. Oh no, I'm not interested in that, what are you talking about? No, no, no, no.
"It's not about how old you are, it's about how you are old. Don't anybody ever retire! Do not embrace old age! It's crap! I haven't got time for that rubbish."
I timidly ask whether the advancing years have made him more contemplative, and I get a similar dramatic slap-down. "Death does not exist," Brian proclaims. "Life is the last word, death is not. All you know now, you’ve known for thousands of years. You’ve always been alive, you’ve never been dead.
"Tell me about death. You see, you can’t tell me anything about it, because it doesn’t bloody exist."
The actor's tones are already recognisable to many under-sixes as the voice of Grampy Rabbit in Peppa Pig.
And now he hopes to encourage many more children's imaginations by writing the first chapter of a story book which primary school classes around the country will finish.
The campaign, by children's education platform BoomWriter, hopes to help schools pay their soaring energy bills by publishing each school’s finished book, which they can sell to raise money. Brian will also select his favourite book and visit the winning school in April.
Brian says his starting chapter is about a boy called Brian Benedict, and based on his own childhood growing up as a coal miner's son in the Yorkshire mining village of Goldthorpe, when it would appear he had just as wild an imagination as today.
"There is a rusty old railway bridge which still exists today, one side has ropes on it and the children used to sail across as the trains went by, and inventing stories and adventures. Brian is a great storyteller and the kids love it, he tells them about newts and dinosaurs and the lost worlds of South America.
"Eventually he tells them a secret, that underneath the Anderson railway shelter in his garden, there is a staircase leading down to a cavern lit up with minerals, and it goes on for miles, and at the end there is a triceratops.
"And he gets on top of the triceratops and travels thousands of miles at the speed of light to the lost world of Venezuela, and finds new civilisations. And it ends there. That's where I've invited the schools to take up the story."
He says he is confident the children will come up with something enthralling. "I have a great love and belief in young people, they're my religion. I'm a child and I want to be a child with them," he says.
"One of my greatest complaints is when teachers say to a student, 'stop daydreaming'. No, daydream, daydream and daydream. Einstein always said that his idea of heaven was a vast gigantic library as big as the Milky Way where you could go and not take the books out. That's my idea of heaven.
"The most I've learned is from children, I love to listen them. Let's see what they've got to say."
With his flamboyance and theatrical delivery, Brian might seem perfectly suited to the world of stage and screen today, but as he grew up it was his fertile imagination which allowed him to dream of a different life as an actor.
He left school at 14 after his father was badly injured in the mines, a shock which gave his mother a nervous breakdown. Brian became an undertaker's assistant, then a plasterer, before getting a scholarship to go to theatre school – something unheard of for a coal miner's son.
His first parts were in shows like Z-Cars, The Three Musketeers and The Avengers, finally breaking into film with a role in 1970's Country Dance, followed by roles including Henry V, Trojan Women and Star Wars. In 1980, he landed his best-known part – as villain Prince Vultan in sci-fi adventure Flash Gordon.
Brian says landing the comic book part was proof that his dreams can come true. He says: "I was brought up with Flash Gordon and never anticipated that I would end up playing Vultan.
"Wherever I go in this world, I can stand on a platform and shout 'Gordon's alive!' and everyone cheers."
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As if to prove the point, Brian then hollers the phrase at the top of his voice. And it's precisely his eccentricity – which he has brought to many roles, including as King Richard IV in the first series of Blackadder – which endears the bushy-bearded actor to millions.
Brian, also a seasoned stage actor and West End performer, even admits "I wouldn't want to interview Brian Blessed" – and his answers to many of my questions leave my head spinning.
Does he still dream of being a grandfather? Brian's actress daughter Rosalind, 46, doesn't have children.
No, my dreams are much more eccentric. My dreams belong to Mars and Jupiter. I think space travel is just round the corner. We've got to find better ways of travelling in space. We belong there.
"I wake up in the morning and rejoice that I’m in a wonderful universe, I rejoice that I’m alive. And I feel that mankind is going to make it."
Brian, married for 44 years to Antony and Cleopatra actress Hildegard Neil, 83, went through astronaut training in Russia in his 70s. He has also made a name for himself as an explorer, and revels in recalling his conquests.
They include becoming the oldest man to reach the magnetic North Pole on foot – when he claims he punched a polar bear – and three attempts to climb Mount Everest without supplemental oxygen. He says: "Every expedition I've gone on, people call me a big yeti, and I think that describes me."
Remembering spending four days with the Dalai Lama in the Himalayas, he chuckles: "I had him giggling, I asked about his sex life. The translator nearly fainted. No one asked his holiness questions like this. He said, 'it's good, I do think of a beautiful woman now and again, then I do my mantras loudly and then take a cold shower'."
Perhaps the most outrageous claim Brian makes comes after he bursts into song with his Pavarotti. "I'm very easy to live with because I’m a very quiet man," he insists. " Kenneth Branagh, who I see every week, says I'm the quietest man he’s met, and it’s true.
"I spend my time thinking, spending time with my dogs, and planning my next projects. I love silence."
For more information go to boomwriter.co.uk/write-to-raise
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