The Duke of Cambridge has paid a personal tribute to the nation's emergency services, speaking of his "profound respect" for its men and women, ahead of his final air ambulance pilot shift.
William also said he had "been so proud to serve" with his East Anglian Air Ambulance (EAAA) crew mates and colleagues and thanked the local community that funds and supports the charity.
His life as a full-time working royal will begin after his final shift ends at about midnight, with the expectation the future king will carry out more royal duties in support of the Queen and his own charity work and causes.
Writing in the East Anglian Daily Times, William said: "As part of the team, I have been invited into people's homes to share moments of extreme emotion, from relief that we have given someone a fighting chance, to profound grief.
"I have watched as incredibly skilled doctors and paramedics have saved people's lives. These experiences have instilled in me a profound respect for the men and women who serve in our emergency services..."
Out of the many emergencies he has attended he highlighted two: "One of the first call-outs I made was to a young man who had committed suicide; it was an incredibly tough day and had a profound effect on all of us, not least in my determination now to draw attention to this issue."
He also mentioned another young man involved in a road traffic accident: "His uncle in the car with him sadly didn't survive, and I was sure that from what we were faced with he wouldn't either - but thanks to the skills of our medical team he is alive today.
"We were first on scene and in such circumstances we all had to pitch in to fight to save the young man's life. It is days like this, when you know you have made a difference, that give you the determination to keep going."
William announced in January he would be leaving the EAAA and has clocked up more than two years flying medical crews to emergencies from a base at Cambridge Airport.
The Duke joined the organisation as a pilot in March 2015 and after completing an initial period of job specific training involving simulator, aircraft and in-flight skills training, he began piloting his first operational missions in July that year.
He has flown as part of a team including specialist doctors, critical care paramedics and pilots providing emergency medical services across Bedfordshire, Cambridgeshire, Norfolk and Suffolk.
Patrick Peal, EAAA's chief executive, said about the duke: "To us, he has simply been another hard-working member of the team; one of eleven highly respected pilots who help us to save hundreds of lives each year.''
On his final day at work William will arrive for a night shift, and attend the handover briefings from the day team as usual.
He will then join his team-mates at the helicopter he has flown for the past two years for a group photograph.