Buying a Christmas present for your 80-something granny-in-law has gotta be tough at the best of times – never mind when the granny in question is one of the world's longest serving monarchs. 

But we reckon that Duchess Kate nailed it back in December 2011 – the year of her marriage to Prince Wills – coming up with a thoughtful and appropriate gift that evidently the Queen loved.

Chatting on a forthcoming two-hour ITV documentary to mark the British royal's 90th birthday, Mrs Cambridge admitted that she was a tad nervous having to come up with a decent pressie.

“I was thinking, ‘Gosh, what should I give her?’

“I thought, ‘I’ll make her something.’ Which could have gone horribly wrong.

"But I decided to make my granny’s recipe of chutney. I was worried about it, but I noticed next day it was on the table.

“Such a simple gesture went such a long way for me.”

Queen Elizabeth II has been on the British throne since 1952 and celebrates her milestone birthday on April 21.