Friends of a 36-year-old Kensington resident whose body was found in the Thames in Berkshire in April, three months after he was last seen in a nearby pub, are embarking on a 50-mile charity run in his memory to raise awareness of men’s mental health.

Property company boss Alexander Stern was described by his cousin James Shrager as an outgoing personality who “loved being around people. He would always go for a coffee at a local coffee shop in the morning and strike up conversations with people on the table next to him.

“He had a very entrepreneurial mind and when the two of us were teenagers, we used to spend hours talking about the different businesses we wanted to start together when we were older.”

However, “Alex struggled with mental health challenges, as have I, as have many people you probably know”.

Mr Shrager, 35, has founded a mental health non-profit, Sidekick, which is marking World Suicide Prevention Day with a month-long campaign, “We all know an Alex”, aiming “to encourage positive conversations around mental health that may help prevent someone from taking their own life.

“In the UK, suicide is the single biggest killer of men under 45. This needs to change.”

Mr Shrager added that his cousin was “missed tremendously by his parents, sister, family and friends”.

The memorial run will start in Berkshire at the weekend, continuing along the river to finish outside one of Mr Stern’s favourite pubs in Chelsea.

Others will cycle a 78-mile route ending in South Kensington or join the runners for the final stretch.

The run/cycle is supporting an appeal for the local rescue team that recovered Mr Stern’s body. It has already almost reached its £20,000 target.

Patrick Timmis, one of the friends taking part in the memorial run, praised Berkshire Lowland Search and Rescue for working “tirelessly” amid “incredibly difficult conditions with almost continual flooding.

“This was a major operation over hundreds of man-hours with helicopters, drones, sonar, dogs and divers scouring the river in Sonning near where Alex was last seen alive.

“We want to recognise their fantastic work and give something back to allow them to continue to help find other missing people.”

www.localgiving.org/fundraising/stern50; www.sidekick.org.uk