Image copyright Getty Images

The Duke and Duchess of Cambridge and the Duke and Duchess of Sussex have teamed up to launch a text messaging service for people experiencing a mental health crisis.

William, Kate, Meghan and Harry have backed the initiative, called Shout, with £3m from their Royal Foundation.

The free, anonymous service connects people experiencing a "tough moment" with trained volunteers.

Prince William said they were all "very excited" about the initiative.

"It provides instant support," he said.

"You can have a conversation anywhere and anytime - at school, at home, on the bus, anywhere."

During a 12-month pilot last year, 1,000 volunteers signed up to the initiative and 60,000 conversations took place.

"That is 60,000 moments when people who were feeling scared, frightened and alone were able to use their phone to connect with someone who could support them," Prince William said at a launch event at Kensington Palace.

The service aims to help people experiencing problems - from suicidal thoughts to bullying and relationship issues - move from "crisis to calm".

The duke also appealed for more people to join as volunteers, who are supported by clinically trained supervisors.

The Duchess of Cambridge said: "For the last few years, I've been focusing much of my work on the importance of prevention in the earliest years of life to help avoid problems in later life.

"But, sadly, for so many, they have already reached a crisis situation."

Kate added that Shout offered crucial support and "the opportunity to turn lives around".

Shout was researched and developed by the Royal Foundation, a charity which the royal couples set up together.

The service operates 24 hours a day, seven days a week and is modelled on the US-based Crisis Text Line, which was launched in August 2013.

Lorraine Heggessey, the Royal Foundation's chief executive officer, said the "innovative solution" helps tackle "one of today's biggest challenges - the increasing number of people needing mental health support".

The Institute of Global Health Innovation (IGHI) at Imperial College London will also work with the project to identify trends and develop insights into mental health to shape the provision of services.