A moving letter from the mother of a young cancer sufferer to author JK Rowling has been read out at a performance in London.

The letter states how the young girl, who died this week, had found comfort in the author's Harry Potter series.

Chrissy Hart wrote the letter to the author last month, saying: "Your words built a castle for her to move into when the prognosis got worse."

It was read out by actress Ellie Bamber at a star-studded performance of Letters Live, a series of performances in which remarkable letters are read aloud.

She wrote: "Your words built a castle for her to move into when the prognosis got worse.

"Mrs Rowling, cancer threatened to take everything from my daughter, and your books turned out to be the fortress we so desperately needed to hide in."

Mrs Hart added "the most important lesson you have taught us" was "for every child that is taken too early, people will come together, huddling close in a big group, wands held high to light the dark sky with the love they felt".

The letter concludes: "You built Hogwarts as a home for her to return to. And for me."

The event is based on the collection of letters published in Shaun Usher's international best-seller Letters Of Note.

The 2016 series will run until Tuesday and feature dozens of other famous performers, including Benedict Cumberbatch, Olivia Colman and Carey Mulligan.Letters Live first launched last year and quickly became a sell-out success.