The founder of Gaydar, one of the world’s first gay online dating sites, has died aged 51.

Henry Badenhorst, who set up Gaydar with his then partner Gary Frisch from their house in Twickenham in 1999, died in his native South Africa on Saturday. He is believed to have killed himself.

“Eighteen years ago, Henry and his partner Gary revolutionised the way that gay men meet and in doing so created a safer environment for LGBT people everywhere,” said Gaydar’s current managing director, Rob Curtis.

“We are shocked and saddened to hear of Henry’s passing and send our sincerest sympathies to Henry’s friends and family.

To Henry. The man who revolutionised gay dating. Our founder and our friend. Thank you for dreaming. You will be forever in our hearts. Gaydar xxx pic.twitter.com/16nhdpHW1v — Gaydar (@Gaydar) November 12, 2017

His death comes 10 years after Frisch died when he fell from his apartment in Battersea, south London, after a night of taking the party drug ketamine. The couple had split up several months previously but remained business partners.

They had moved to London from South Africa in 1997 to set up the IT firm QSoft, which provided revenue-management systems for airlines.

In 2009, Badenhurst explained to the Guardian how the pair came to set up Gaydar.

“It was June 1999,” he recalled. “We had a Dutch friend called Frank who was single and said: ‘I need a boyfriend – can you help me?’

“We put him on Excite [a search engine] which had a dating section where you could upload a picture. But it took two weeks for him to get a response, so we said that we were sure we could create something specifically for the gay market.”

By November the same year the site had launched. It went on to become one of the most popular dating sites for gay and bisexual men, starting as a desktop-based website before launching an app in 2009.

Its influence was such that its role in facilitating gay dating has been regularly acknowledged. In 2006, Badenhorst and Frisch were jointly placed at number three in the Independent’s “pink list” of the most influential gay people in the UK because of the way their work revolutionised the way gay men and women meet each other. From its humble beginnings, it grew into a portfolio of websites and an award-winning radio station.

Badenhorst, who was born in Johannesburg, left the company in 2013 after it was bought by the Big Breakfast creator, Charlie Parsons.

The exact circumstances of Badenhorst’s death remain unclear.

In the UK the Samaritans can be contacted on 116 123. In the US, the National Suicide Prevention Lifeline is 1-800-273-8255. In Australia, the crisis support service Lifeline is on 13 11 14. Other international suicide helplines can be found at www.befrienders.org.