Sabrina Cohen-Hatton has gone from rough sleeping as a teenager to visiting the Prince of Wales in Windsor Castle to give him advice on tackling homelessness.
She was able to give her own story to Prince William as proof that homeless people should not be "written off".
"I sit in front of you now with a job, a home, a family and a PhD," said Sabrina, who works as a fire service chief.
Prince William marked the first year of his Homewards project with a visit to Lambeth in south London where he pleged: "It is possible to end homelessness."

The prince delivered the message that there is nothing inevitable about homelessness and that it shouldn't be normalised.
Meeting Homewards representatives in Brixton he said: “Homelessness is a complex societal issue, and one that touches the lives of far too many people in our society. However, I truly believe that it can be ended."
He spoke of the importance of "shifting perspectives" about homeless people and the need to "focus on prevention, rather than simply managing the crisis".
Homewards is a five-year project based around six areas around the UK.
That includes Newport in South Wales - and as a 15- and 16-year-old that was where Sabrina was sleeping rough, after the death of a parent and problems at home.

Her way out was selling the Big Issue - "I credit them with saving my life" - and once she had secure accommodation she was able to get a job in the fire service, which became her career.
She used this "lived experience" to tell Prince William and the Homewards project about what was needed.
"There were lots of closed doors in my face," she said. Even when support was meant to be available, she said in practice it could be hard for homeless people to have the confidence to access it.
Or there can be practical barriers. She said she relied on her dog, called Menace, but many hostels wouldn't let people stay with pets.
Sabrina also warned of how homelessness was linked to the "pernicious" long-term impact of poverty.
She went on to become chief fire officer of West Sussex and has spoken widely about her own journey, including this latest role as an advocate for Homewards.
Sabrina said Prince William showed a lot of "empathy" towards the issue of homelessness, which she suggested reflected some of the "trauma" in his early life.

At the event in Brixton, Sabrina spoke alongside Chris Lynam, who recalled the intense "loneliness" that accompanied his own homelessness and drug addiction.
"It's a very isolating experience... society is quite hostile to homeless people," said Chris, who is now supporting Homewards' work in Sheffield.
Prince William described it as an "honour" to hear Chris talk about his experiences.
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