King Charles has featured in a surprise birthday tribute to David Attenborough, with a cast of wild animals helping to relay his handwritten congratulatory centenary card.

The whimsical film, A Very Special Delivery, begins with the king writing his tribute in the library of Balmoral Castle. Charles, wearing an animal-themed tie featuring elephants, reflects on more than 60 years of friendship with the renowned naturalist.

As he writes, Queen Camilla’s rescue dog Moley scampers around his desk. The signed card is then borne on a silver salver by a butler to a waiting Land Rover. But disaster strikes. A fallen tree blocks the vehicle and what unfolds is a rescue mission by a roll call of heroic animals.

A border collie called Flynn takes off with the envelope in his mouth and a relay of birds and animals then carries, ferries and flies the card from the Scottish Highlands to towns and waterways across Scotland and England. At one point the card is carried wedged between the spines of a hedgehog.

Eagles, a red squirrel, a flock of geese, an otter, a swan, a duck, a fox and a deer all play their part before, finally, a barn owl called Lily delivers the by-now tattered, travel-worn card through the letterbox of Attenborough’s London home.

The four-minute film, which premiered during the live gala tribute to the renowned naturalist at the Royal Albert Hall on Friday night, was produced by BBC Studio’s natural history unit.

The king’s relationship with Attenborough dates back to 1958 when the then nine-year-old prince and his sister, Princess Anne, visited the set of the BBC children’s programme Zoo Quest.

In his card, Charles wrote: “It is amazing to think that you and I have known one another for more than 60 years; indeed, I believe we first met in 1958, almost a decade before the age of colour television, and of course our paths have crossed many times since.

“Over those decades you have revealed the beauty and wonders of nature to audiences around the world in new and marvellous ways. In so doing, you have shared my determination to highlight the urgent need to protect and preserve this precious planet of ours – and all Life on Earth – for future generations.

“Thank you, then, for all that you have done. And on behalf of the whole nation, I wish you a very happy 100th birthday. Charles R.”

A Buckingham Palace spokesperson said: “His majesty was delighted to feature in this special tribute to a man who has shared his lifetime commitment to the natural world, and has followed each stage of the filming process with great interest. He was only sorry not to meet Lily the magical barn owl in person.

“Her majesty [Camilla] was particularly touched that her mischievous Moley was invited to make a cameo appearance and was on hand with a ready selection of dog treats to help coax a willing performance on the day.”

Mike Davis, an executive producer at BBC Studios natural history, said making the film was a “labour of love”. “It needed to be a roll call that felt rich and varied and accurate, in terms of where the animals would be on each leg of the journey, but there were also much-loved British species we wanted to include, like the eagle, hedgehog or fox.”

Charles also wanted to feature some of his favourites, such as an owl and a red squirrel. “There was also the practical factor of whether they could realistically carry a letter, which ruled out certain smaller animals on our longlist,” Davis said.

As film-makers were “not constrained by the usual rules of natural history film-making, or indeed reality”, the brief was to “have fun and entertain”, he added.

Jack Bootle, the BBC’s head of specialist factual, added: “Sir David has spent a lifetime championing the natural world, so it seemed fitting that the natural world should do something to say ‘thank you’ in this unique birthday tribute.”