Sir Christopher Gent created the world's biggest mobile operator butat what cost?

Sir Christopher Gent has failed to keep his New Year resolution. The chief executive of Vodafone promised himself - and his family - he would not be at his desk before 6.30 each morning.

But the 54-year-old boss of the world's largest mobile phone company is often the first in at London Road, hub of the sprawling network of Vodafone offices around Newbury in Berkshire.

In the next few weeks, he will close the door on the shabby town-centre headquarters with its flock wallpaper, worn carpets and boardroom beside the car park.

The management team will relocate to a large new complex outside Newbury, where he will occupy a smart new suite - albeit briefly.

"Chris is determined to move in, even though he will be moving out before long," says one colleague. He is retiring in July.

After spending 18 years at the company - the last six as chief executive - Sir Christopher delivers a robust defence of Vodafone's strategy. Sitting in the old boardroom, he says it is the world's dominant mobile operator. Behind him there is a framed reminder of Vodafone's humbler past - a 1980s listing certificate for Racal Telecom.

Twelve years after Vodafone demerged from Racal, Sir Christopher is also ready to part company. Chief executives, he suggests, should not stay on beyond their "sell-by date".

He adds: "There was a famous story of George Eastman at Eastman Kodak. He worked to 79, and then committed suicide. The suicide note said 'My work is done, why wait' - that is not me. I've seen too many people not hand over while they still have mileage in the tank... it's about hopefully handing over a decent legacy."

The Gent legacy will be inherited by Mr Arun Sarin, a Vodafone non-executive director and former chief operating officer of AirTouch, the US telecoms group that was acquired by Vodafone in 1999. Mr Sarin will shortly begin shadowing the outgoing chief executive and reviewing his strategy.

Sir Christopher denies being the sole standard-bearer for that strategy, which has seen Vodafone spend £170 billion (€253 billion) on acquisitions and focus on mobile operations.

"First of all I don't like the 'I' word," he says. "We develop a strategy as a consensual process among the most senior business executives. We look at it every year, test it, revise it, execute it."

If credit is due, the chief executive says it should be for developing "an effective" platform for Vodafone's future. But it has not been achieved without cost. The company and Sir Christopher have faced criticism on several fronts: over acquisitions, a £15 billion investment in third-generation mobile licences and executive pay.

Sir Christopher, however, says he has been vindicated. Vodafone has survived the technology downturn in far better shape than rivals such as Deutsche Telekom - partly by using shares rather than cash for acquisitions. It has stripped out costs and sold non-core assets from acquisitions such as AirTouch and Germany's Mannesmann. It has also begun the introduction of 3G services.

On all of these issues, Sir Christopher says Vodafone has confounded its critics.

But he is not complacent and still nurses bruises over the cost. In particular, he criticises the 3G auction process, which saw Vodafone pay £1.5 billion more than intended for its UK licence.

Sir Christopher insists that Vodafone had to participate in the auctions. It could not afford to be left without a 3G capability. But the chief executive recalls: "We knew it was going to be a bad outcome because the UK government and the German government distorted the process, so it was not open and transparent."

Having got the licences, he promises Vodafone customers a seamless user-experience across the globe. "Our ambition when we set out our strategy over five years ago was to establish a world-leading position for the company. Being in the most significant countries around the world was a fundamental requirement for what I call a defensible market advantage."

That position was achieved mainly through the acquisitions of AirTouch and Mannesmann. Shareholders, of which there are 443,548 in Ireland, initially welcomed the deals, although there were later complaints of destruction of shareholder value.

Sir Christopher brushes that suggestion aside. "There is always controversy over 'Did you pay too much?' But if you are using shares to buy an asset, if there is inflation in that asset, there is almost certainly inflation in the shares you are using to buy."

He argues that the deal created value because selling non-core Mannesmann assets - including Orange and Ruhrgas - realised more than £40 billion. "Anyone could take a snapshot and make a comment. Far from destroying value, I think the transaction created value." Certainly Vodafone would not boast a global footprint without Mannesmann or AirTouch. But Sir Christopher admits there are still holes on the map.

At the end of last year, Vodafone was out-foxed by Vivendi Universal of France in the battle for control of Cegetel, their joint venture behind the country's SFR mobile operator. Although Vivendi wrested control of Cegetel from Sir Christopher's grasp, Vodafone has still ended up with 30 per cent of the holding company and 44 per cent of SFR itself. He fully expects Vivendi to sell out to Vodafone when, rather than if, it decides to exit that business.

He is also relaxed about the group's US presence, where AirTouch has been folded into Verizon Wireless, the country's leading mobile operator. Vodafone holds 45 per cent of that business. Contrary to speculation that Vodafone might exit Verizon, Sir Christopher expects the tie-up to continue, allowing the introduction of new US services.

He says that Vodafone shareholders understand and support the position the company finds itself in: a global strategy in place; 3G licences secured - albeit at a high price; and management succession resolved.

Vodafone's performance measures are more onerous that most US companies demand. But Sir Christopher insists that Mr Sarin, currently the chief executive of California's Accel-KKR telecom group, knows just what he is getting into.

"He's that much younger so he's got mileage in the tank to continue to drive the business forward at the level of intensity it requires."

As for his own future, Sir Christopher is coy will not be drawn."There's things that I want to do. That's for me to know and you to wonder."