THE last time I visited the marbled splendour of the Institute of Directors in Pall Mall, they threw me out. I wasn’t wearing a tie. That was 10 years ago and, as I’m not keen on neckwear, I haven’t been back until now.

How times change. “Have you been to our premises at 123 down the road?” says George Cox, looking suddenly animated. “If you walked in there, you’d feel really at home.” Sushi bar, plasma screens, plugs for your laptop, trendy young receptionists.

“We got Wayne Hemingway to design it,” grins Cox, “and Tony Blair to open it. If you’re from the media, fashion or technology industries, I think you’d feel it’s your kind of place.”

Cox, 64, who steps down as director-general of the IoD next month, is a bundle of strange, clipped enthusiasms. With his brusque approach, militaristic manner, and bursts of staccato speech, he seems more suited to running an officers’ club — the site’s former incarnation — than overseeing the IoD’s current all-purpose brief: lobbying group, meeting place and professional standard-setter combined.

But appearances can deceive. Cox, a computer-services boss by background and a moderniser by instinct, has spent the past five years trying to drag the IoD into the 21st century. As a former head of Unisys’s UK arm and founder of Butler Cox, the tech consultancy which he sold to Computer Sciences, the American giant, in 1991, he has no need to work — he just likes the challenge.

And, as a radical in conservative clothing, he has perhaps proved a surprise for the business bigwigs who appointed him. It’s not just that IoD offshoot for media trendies. There have been new premises launched in seven other cities, plans for the IoD’s first overseas site in Paris, and a “chartered director” programme offering accredited assessment of board-level competence.

IoD membership has also leapt (from 48,775 in 1999 to 53,000 this year), a remarkable achievement for a century-old institution that many felt was a crusty dinosaur.

So pats on the back all round? Not quite. The end of Cox’s reign has been accompanied by a blitz of criticism from an older generation of bosses who claim he has gone too far, especially in building close relations with New Labour. They also dislike his emphasis on the facilities side: “Regus with restaurants”, as one sniffily put it to me.

Last year’s removal of the high-profile policy director Ruth Lea, a vociferous critic of the government, was the final straw. Former IoD top brass have since lined up to fire a volley of parting shots at Cox. Ex-IoD president Lord Young of Graffham even called him a government “patsy”.

“Yes, that was rather charming,” says Cox, sitting in his fifth-floor office, “and I have avoided any response to what was an orchestrated campaign. But the IoD has changed enormously over the past five years, and I’m keen that as an organisation it’s seen to have changed because, frankly, before all that, a lot of people didn’t join.”

And guess what? he adds. While those insults were being thrown earlier this year, membership applications surged again. “So maybe,” he adds drily, “we should get David Young to keep working at this.”

He has a point, but so do the old guard, who have been appalled at how the IoD’s lobbying arm, once a trenchant opponent to Labour, has gone quiet. Did he squeeze Lea out to appease his new friends in Westminster? Cox sighs. “Come on,” he says, “It may be flattering to Ruth to think there is a No 10 plot, but really . . .”

As for Lea, he has never discussed her departure — part of a legal agreement both parties signed — but the whole thing was blown out of proportion, he says. If you look at the objectives he was set when appointed, including boosting the IoD’s lobbying clout and building membership, he has hit every one.