Cressida Bonas' sister has been diagnosed with an inoperable brain tumour

She told the Daily Mail's Femail: "It hasn't been easy. It's been so painful at times and so traumatic me and for my family. My mum keeps saying I should write a book, maybe one day.

"My family has been very supportive. We're like rocks to each other. I'd feel lost without [them].

"My mum is amazing. She's a proper queen bee to all of us and my relationship with my sisters and my brother [Jacobi Anstruther, Georgiana Anstruther, Isabella Branson and Cressida] is just... we'd do anything for each other.

"We tease each other a lot, but we really love each other.

"I can't imagine not having such a lovely family, I don't know how people cope. It's been really nice for me to have them all and honestly, they did not leave me alone.

"When I came out of hospital, the doorbell was going all the time."

While doctors cannot operate on Pandora, she is being treated with immunotherapy and is feeling positive.

She said: "To operate they'd have to go through blood vessels and that's not great.

"So they categorically said in the first meeting "I'm really sorry, but we can't."

"They said that chemotherapy won't help me, but immunotherapy might really work. So I've done two doses.

"There are a few side effects, but it's hard for me to really know what they are because I've got so many other things going on. I'm in intense pain if I don't take a lot of very strong painkillers.

"In the last few months, I probably have been the closest to feeling depressed than I've ever been and I'm not a depressive person.

"That's been quite scary. There have been days where I've been like I can't bear the pain. But then there's something in me that bounces back."