Prince William has joked about his most used emoji - suggesting that it is the rather rude aubergine.

The royal, 41, made the quip while he and wife Kate Middleton, 41, were being interviewed for BBC Radio 1's Going Home show, prompting one of the hosts to reportedly say he has a 'dirty mind'.

When host Vick Hope asked the Prince and Princess of Wales which of the characters they use most frequently, William quipped: 'Is this a clean thing? Is it a family one?'

Meanwhile Kate joked: 'It depends what group, if it's the family WhatsApp group.' 

William continued: 'I've been told not to pick the aubergine, so I've got to pick something else.'

He added: 'It would have been the aubergine, but I'm saying now because I've got to be a little grown up that it's the one with the eyes [that] go up and down, and the mouth.'

Revealing her emojis of choice, Kate said: 'It's got to be the heart, with then the crying emoji, the sort of like hysterical laughing when things go wrong.'

Show hosts Jordan North and Vick Hope appeared both shocked and delighted at William's response. Jordan said: 'He said the aubergine emoji, this is brilliant.' 

Meanwhile Vick is reported as saying: 'He knows. He’s got a dirty mind.' 

The conversation then moved on to safer topics, with the royal couple discussing their dinner plans. Revealing that they were planning to enjoy a curry, William admitted he cannot eat anything too hot. He said: 'I can’t do too much spice, I start sweating. It’s not attractive.'

However, Kate said: 'Whereas I like the spice so I have to sort of cook the curry and then add the extra spice at the end.'

William then quipped: '[Kate] has to bring it in gently because otherwise I get too sweaty. It’s not a nice sight.' 

The interview took place on Tuesday, as the Wales hosted a forum, Exploring our Emotional Worlds, in Birmingham to mark World Mental Health Day. 

They teamed up with BBC Radio 1 as well as charity The Mix, as they brought young people together to talk about mental health.

Speaking during the event, Kate told the crowd that she and her husband are 'inspired' by how open young people are in speaking about wellbeing. 

She said: 'Today, more people feel empowered to talk about their mental health than ever before.

'This is a major step forward. William and I continue to be inspired to see young people, like you all here today, leading this charge - being particularly brave in having some of those conversations yourselves. 

'As a generation, you value and talk more about your mental health than any before you - something we truly admire and applaud.'