Five Guys UK operation director Marcel Khan has celebrated the “brand promiscuity” of millennials and welcomed choice in the better burger market.

Speaking at MCA’s Restaurant Conference, Khan appeared in the week Five Guys opened its 50th UK restaurant in less than three years – the equivalent of opening a site every 21 days.

Joking that the aggressive rollout had been “very tiring”, he put the US-founded concept’s success in the UK down to the quality of the product – and admitted it was always looking for ways to inspire staff.

He said: “This idea about millennials and brand promiscuity… having lots of different burgers to try is an amazing thing. Burger monogamy is not a good thing. Burger promiscuity is.”

Explaining Five Guys’ approach to people, Khan said: “I don’t think we’re people-led, I think we’re a product led company. You need amazing teams to deliver a great products and you need to believe in the product. You end up with a greater people culture when you have something to believe in.

He continued: “I do worry we don’t do enough for our people. I would love to be able to say we’re perfect, but we’re not and I think questioning things is the source of our strength.”

Khan said Five Guys had tried to demystify and simplify potential career options and had a culture of continuous improvement.

Positively inspiring staff to work hard – which includes hand making all its food every day, and a two hour deep clean late into the night – was crucial, he said.

“It never ceases to amaze me when you walk into a restaurant and you see bosses walking around being grumpy”, he added. “I don’t know how to inspire and motivate and be grumpy at the same time. The power of positive behaviour is incredibly important.”