Princess Diana once threw the cheekiest birthday party for Prince William

Proof that she had the best sense of humour

Yesterday Prince William celebrated his 36th birthday by carrying out his royal duties, as per usual. But his birthday weren't always so work-focused.

Princess Diana famously invited supermodels to the palace for her eldest son's 13th birthday – but her former head chef Darren McGrady has revealed her sense of humour didn't stop there for the occasion.

'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.'

However, inviting supermodels to meet her teenage son wasn't the only trick up Diana's sleeve – she had something much funnier planned.

'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!

'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.'

Hilarious.

'[Diana] 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.'

We're sure the whole thing is one of William's many treasured memories about his mother and her cracking sense of humour.