People often wrongly dismiss the pain and stress being an entrepreneur can bring, according to Outsourcery co-CEO and former Dragons Den investor Piers Linney.

Speaking at the Santander SME Summit London 2015, Linney told Times business editor Richard Fletcher he himself had experienced several “squeaky moments” in his time as an entrepreneur and that he could identify other entrepreneurs by “the pain in their eyes”.

“There is a lot of stress on personal relationships when you are trying to make your business a success,” he said. “You stop getting invited to parties and spend a lot of time on your own in the early days – so it can be a very lonely existence”.

Linney left his job in the City in 2000 and used his final bonus to set up his first company. He says that a sign of the difference in investment climate today and then is that he made £700,000 “leaving the building” when he told colleagues about his new internet venture. “That would never happen now,” he explained.

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But despite seemingly overnight success, he added that he had had periods of doubt and financial stress “ever year” since becoming an entrepreneur and investor. And he warned those looking to follow in his shoes that they must be prepared to put up with the long hours and personal challenges.

“Entrepreneurs must be willing to put up with the difficulties and a path that may meander over the years,” he said. “If you’re not prepared to work at your business 18 hours a days, seven days a week for 10 years, maybe you should think about doing something else.”

He also warned that those who wanted to succeed needed to be prepared to make very tough decisions – sometimes at the expense of friendships and relationships. But those who make those sacrifices have the best chance of success.

“One day you might have to make the decision to sack your best friend or your best friend’s wife,” he said. “But if you’re prepared to make those decisions you will survive.”