Watch: Lenny Henry discusses his first experience of The Rings of Power
The 64-year-old British comedian plays Sadoc Burrows in the TV show, who is an elder of the Harfoots — the predecessors of Hobbits.
Set thousands of years before the events of the Lord of the Rings novels, the show follows the events of the Second Age, including the rise of Sauron and the forging of the titular rings.
"It was a real grounding in everything to do with Tolkien and his world-building," Henry told Yahoo Entertainment UK.
Henry revealed that his first "immersive and wonderful" day on the New Zealand set proved to be a revelation when he saw the amount of work that had been put in by the crew.
He said: "I didn't have a script and I was a bit frustrated that I hadn't seen some of the episodes and I wanted to know what the story was.
"The production manager said 'come with me' and he walked me through the story by showing me all the prop swords, shields, the Harfoot clothes, bits of set, staffs, books.
"By the time I got [through it], I was like 'I want to be in this show!' It was so exciting to see the amount of invention that had gone into this world."
Henry said the story behind the new series will be "very exciting and anticipatory" for fans new and old, exploring a period of Tolkien's history that has not yet been explored in any adaptation.
"It's a Tolkien primer. It's great. A thousand years before canon, so you get to see the rings being formed," he said.
Henry added: "You get this idea that we're all at peace but something's on the horizon.
"All of the ducks are getting in a row, all of the chess pieces are being put in place and there's evil but there's also magic and the means to fight that evil."
Markella Kavenagh portrays young Harfoot adventurer Nori and said the cast had access to JRR Tolkien expert Griff Jones if they needed help with details about Middle-earth.
She added: "As a cast as well, we would find things out and share information. The showrunners are really knowledgeable too, so it was nice to have that context before."
With so much lore to handle, the task could be daunting for cast members, but Benjamin Walker — who plays elf leader King Gil-galad — said this was part of the thrill of the job.
"Why wouldn't you want to be [across the lore]? Part of the job is that we get paid to read and study Tolkien. This is a great job," he said.
Walker added: "Amazon has assembled a team for you. If you're new to this, you can talk to Griff Jones and you can really do a deep dive.
"You can really get in there. Any kind of question you might have, there is an answer. But I garner such pleasure from immersing myself in his writing that I'd be doing it anyway."
Walker's co-star Charles Edwards, who portrays elven smith Celebrimbor, said he felt it was important to put in the work in order to live up to fan expectations and the heft of Tolkien's universe.
He said: "You'd be doing a disservice not to do your work. Particularly with these characters, many of whom are new to the screen for the first time but are hugely revered by fans who know their stuff.
"There is such a weight of respect and love for the material on set and in the finished product. To not be as prepared would be a mistake."
Dylan Smith, who plays Nori's father, said the cast were able to feel safe to take creative risks thanks to the level of Tolkien fandom on set, protecting the established canon.
He said: "I did feel there was also encouragement to offer up and create a new world, within a very defined existing world, and bring your biggest imaginations.
"There was such architecture protecting the Tolkienism of everything. You never felt unsafe that you were going to come up with something that was gonna be left-field."
But the cast were keen to stress that this is not a show geared solely towards Tolkien superfans, with Cynthia Addai-Robinson — who plays Númenórean leader Míriel — keen to introduce her family to Middle-earth through the show.
She said: "I have a lot of nieces and nephews and I'm excited for this adaptation to be their introduction to Tolkien. The best case scenario is that it sparks excitement in them and then they go to the books and the original source.
"My mother, who is not familiar with this material, I'm excited for her to watch and enjoy something like this. This adaptation is an invitation to all. We want to be including everyone and inviting everyone into these stories because there's plenty for everyone to get into."
The Lord of the Rings: The Rings of Power premieres on Prime Video all over the world on 2 September, with weekly episodes released thereafter.
Watch: Trailer for The Lord of the Rings: The Rings of Power