Prince William talks about his mental health during his time with the air ambulance

Prince William has long been an advocate for talking openly about mental health, starting initiatives like Heads Together with Kate Middleton and Prince Harry, and opening up about the struggles he faced when his mother, the late Princess Diana, died when he was just 15 years old.

Last week, William decided to talk about his mental health while he was working as a pilot for the East Anglia Air Ambulance from 2015 to 2017.

During a trip to Belfast to mark Emergency Services Day, the Duke spoke to emergency first responders about witnessing traumatic situations on the job, saying: 'I couldn't put my finger on it, but you just felt very sad.

'For me it was the sadness, I really felt the sadness, I'd absorb the jobs I'd gone to.

'Sadly with the Air Ambulance you get a lot of deaths and I didn't realise (the impact) - I would go to the next one and the next one.'

William met leaders from emergency services in the UK, setting up the Emergency Responder Senior Leader Board to encourage open conversation about mental health and how to offer emotional support.

In a speech at the Police Service of Northern Ireland's training college, he said: 'I know first hand, that even in routine circumstances, those of you on the frontline can face immense challenges that can naturally have a significant impact on both your physical and mental health.

'Firstly, it's important that we recognise that. And secondly, it's important that we do all we can to support you through it.'

The royal also met volunteers during a training exercise to find missing people, and told them: 'You're the ambassadors for the community, thank you so much.

'You are the foundations of the community, you are the backbone of that...that's not to be sniffed at, that's something very special.'