This is the rude (and hilarious) birthday card Diana once sent her accountant

Ha!

When it comes to Princess Diana, everybody feels as though they knew her in some way. From the reason she kept her head down in public, to her second secret wedding dress, we feel as though we know so much about her.

But there's one thing that we can all be sure of - Diana had a brilliant sense of humour. According to her former butler, Paul Burrell, she was particularly fond of buying her sons joke presents for birthdays and Christmas.

'She'd spend hours looking for jokey things for their stockings,' he once said.

'One year, Harry got fake dog poo.'

And now there's even more evidence that Diana was a bit of a joker. In fact, the proof is going on sale at auction to the highest bidder.

A birthday card that Prince William and Prince Harry's mother once sent to her accountant, Anthony Burrage, has piqued the interest of many due to it's rude and hilarious nature.

The cover shows a woman sleeping next to a spindle, alongside the writing: 'A little prick in the hand sent Sleeping Beauty to sleep.'

The punchline lies inside the card, reading: 'Only the big ones are worth staying awake for!'

Diana had written to her friend: 'Tony, a belated Happy Birthday for the 5th! From, Diana.'

The card, which will be sold at Julien’s Auctions, is expected to earn somewhere between £600 - £900.

The individual who currently owns the item is said to have received it from a collector of Diana's things. However, they are now selling the iconic card, which was originally set to go on sale for £152.

Former royal head chef Darren McGrady previously revealed that Diana's sense of humour didn't stop at gifts - she threw William a rather cheeky 13th birthday.

‘I remember that day really well because she told me they were coming. I was super excited and I wanted to meet them too but I didn’t get the chance,’ he told HELLO! online.

‘It was Claudia Schiffer, Christy Turlington and Naomi Campbell.’

As if that wasn't enough, Diana also had another trick up her sleeve.

‘I came into work that morning and went down to the refrigerator, opened the door and I was just confronted with the biggest pair of boobs I’ve ever seen in my life. The Princess had ordered a boobs cake for William’s 13th birthday. I wish I’d taken a photograph of it!' he continued.

'I didn’t know anything about it, I just thought, “Oh my gosh.” I asked the butler, “What on earth is this?” and he said the Princess had ordered it for William’s birthday. [She] loved embarrassing people in the nicest way, in a fun way, whether it was telling a dirty, risqué joke – which usually got me. William just went bright-red.'

Bless him.