Speaking to royal biographer Robert Hardman for his new book Our Queen, the Prince told how the Queen stepped in to help, after he went to her for advice.
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"I came into the first meeting for the wedding, post-engagement, and I was given this official list of 777 names — dignitaries, governors, all sorts of people — and not one person I knew," revealed the Prince.
"They said: 'These are the people we should invite.' I looked at it in absolute horror and said: 'I think we should start again.'"
His grandmother agreed, telling him to 'bin the list'.
"I rang her up the next day and said: "Do we need to be doing this?"
And she said: "No. Start with your friends first and then go from there. And she told me to bin the list," he said.
"And it's advice like that, which is really key, when you know that she's seen and done it before."
One point that was non-negotiable was his wedding outfit.
"I was given a categorical: 'No you'll wear this," recalled the groom.
The striking red outfit that made such an impression in Westminster Abbey reflected his position as Colonel of the Irish Guards, his most senior military rank, to which he had just been appointed by the Queen.
His comments about being bossed about are rather tongue in cheek. No one observing the Prince as he nears his 30th birthday can fail to notice that he is very much his own man.
Meeting victims of Australia's floods and the earthquake in New Zealand last year on behalf of the sovereign, the second-in-line to throne radiated charisma and won people over with his unaffected style and sincere concern.
Reflecting his modern take on monarchy, William wore chinos and an open-necked shirt for the five-day visit.
He won praise Down Under and closer to home.
"The Queen sent me the most wonderful letter saying 'Congratulations' and 'Well done, you did well down there', which meant a lot to me.
"It's funny, but when you get a letter from her or a bit of praise, it goes a long, long way, more so than anyone else saying 'well done' to you.
"It's mainly because there's such gravitas behind those words."
The future King – who apparently wants to delay life as a full-time royal in favour of continue his RAF career – finds it hard to believe that at his age, the Queen had already been on the throne four years.
"Back then there a different attitude to women. Being a young lady at 25 – and stepping into a job, which many men thought they could probably do better – it must have been very daunting.
He marvels at her grace and resilience under pressure.
"You see pictures of her and she looks calm, she's poised, she's elegant and she's all the things she needs to be at 25.
"You present her with a challenge and she'll (get on) with it. And I think to be doing that for 60 years, it's incredible."