But as chief executive of LA Fitness, a chain of 67 health clubs that has been on and off the stock market, he has proved himself more than just a muscle-man. He floated the business in 1999 for £55m when it was 15 sites strong, and took it private earlier this year — selling the group to MidOcean Partners, a huge private-equity fund, in a deal worth £90m (£141m including debt).

Cape Town-born Turok remains as boss and, backed by his new MidOcean chums, is now plotting to buy up rivals. Top of his list could be Fitness First, the UK’s biggest chain, which has 400 clubs worldwide and whose own private-equity backers recently signalled their intent to sell.

In the meantime Turok, ever the entrepreneur, can polish up the £14m he is estimated to have made from taking LA Fitness private. Not bad for a former PE teacher — but looking at him, you wouldn’t want to pick an argument.

“Yes, I have banked money,” he says with a small smile, “but I also have a percentage of the institutional investment in LA Fitness which invests pari passu with MidOcean. My equity component is realised only on the success of the business, which is typically how venture capital works.”

He raises a quizzical eyebrow to check I have understood. Forget the muscle; Turok, 50, is nobody’s fool. An émigré from South Africa with tangled Latvian Jewish and Irish Catholic roots — his father, Ben Turok, is a white African National Congress (ANC) activist, twice imprisoned by the apartheid regime — Turok has fought dyslexia and prejudice to get to the top of the UK business pile, and he’s not climbing off any time soon.

Sitting in his decidedly unglamorous head office, a sweaty collection of cubicles carved out of a clothing warehouse in London’s East End, he is master of all he surveys — which is quite a lot, since he installed windows in the internal walls so that he could watch what his fellow executives are up to. “Very useful if you want to summon everyone to meetings,” he grins.

That’s Turok’s style: low- cost, sales-driven, very hands-on. Others describe him as a gritty survivor. He learnt the ropes from club entrepreneur David Lloyd, before building up his own business single-handedly and running it without delegation.

He has done that through boom times and more recently during a downturn, when debt and over-hasty growth made profits scarce for many fitness chains, and one by one they came off the stock market.

Turok’s clubs — medium-sized, always a gym and a pool, around £37 a month to join — have performed better than most, so while other fitness bosses have left the locker room for good, he is still pumping on.

He also survived a bad motorbike crash in 2002, which left him with a slight limp, so you can say he has had it from all sides. Yet he remains jovial and determined, a bundle of energy still with his eye on the prize.

The question now is, how will he work with his new partners?

“There is a natural relationship between myself and MidOcean,” he nods. “They have tremendous commercial acumen and knowledge of the industry through their parent in the US, where there is a more mature fitness market. They also have knowledge of member acquisition and retention in the UK through their other investments. So what we got was a smart investor.”

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