Paul Brennan moved from Ireland to join Citigroup's London trading floor in 2007 after graduating in Economics from Trinity College, Dublin. It took 10 years before he felt comfortable enough to be open about his sexuality to his colleagues.

“It was towards my late 20s when I realised I was gay, and at that stage I didn’t feel comfortable being out on the trading floor — it just felt like there was no one else,” he told Financial News. “In my mind, I felt like I had to make a choice between being successful in my career or being out as a gay man. I chose to stay in the closet.”