TANK commander, motorbike racer, advertising agency director and, for nearly half a century, observer and commentator on the motor racing scene, Murray Walker is genuinely multi-faceted.

His high-revving television delivery is to Formula One what Dan Maskell's hushed and silver tones were to Wimbledon's Centre Court and Bill McLaren's Borders burr is to the Five Nations' rugby-football campaign.

Away from the pressure-cooker environment of a Grand Prix trackside commentary box, Murray Walker OBE is an interviewer's dream, candid, eloquent and patient with an almost photographic recall about his life and a consuming hobby, which he shares enthusiastically with millions of armchair Grand Prix racers every other weekend.

On a rare off-duty Sunday afternoon, a call to his Hampshire village home brought a breathless, car-washing Walker to the phone with the firm, but polite suggestion that we delay the conversation for one hour until his BMW 328i Sport was rendered spick and span.

The 73-year-old former AJS racer and Norton trials rider, whose experience included the Scottish Six Days Trials near Fort William, only recently disposed of a pair of BMW motorbikes on the basis of: ''Unless I rode regularly I reasoned I should not ride at all. It requires total commitment.''

Walker finally became a full-time commentator in 1982 when the beloved hobby took over completely from a long-standing directorship of what was originally Masius Wynne-Williams, a major ad agency whose clients included Mars, British Railways, the Co-op, General Motors and Beechams.

Walker said: ''I have been incredibly lucky to have a hobby, which I could indulge so completely and run parallel to my full-time job.

''No I did not pen 'PAL prolongs active life', or 'a Mars a day helps you work, rest and play' and 'Trill makes budgies bounce with health' although they have been credited to me,'' admitted Walker, who moved into advertising after distinguished war service. He saw sustained action with the Edinburgh-based Royal Scots Greys, the last cavalry regiment to be mechanised, fighting from Normandy, across Holland and Germany, before the link-up with the Russians in the Baltic port of Wismar.

There is a certain upright, military bearing about the stocky barrel-chested Captain Walker (retired), who after successful hip joint replacement operations maintains twice-weekly workouts at a local country club, accompanied by his equally active wife Elizabeth (nee Conway-Allan), daughter of a Master of Surgery at Glasgow University. This fitness regime is vital to Walker ''keeping on the ball, keeping agile mentally and physically'' and coping with a challenging 17-race global routine.

When ITV gazumped the BBC last year to secure Grand Prix coverage rights in Britain there was anxiety in F1 land about whether or not The Voice would be transferred or indeed fit into the new, more comprehensive and populist coverage.

Head of BBC Sport Jonathan Martin could have been churlish and invoked Walker's rolling contract, which did not expire until May this year, but instead kept him on board to commentate on the British Touring Car Championship.

By having a non-exclusive ITV deal, Walker straddles both channels and racing disciplines, equating to Bill McLaren covering Rugby Union and League for BBC and Sky respectively.

The second issue was who would ride shotgun alongside the man who first broadcast live TV broadcasts from an English motorcycle hill climb in 1949, the year he made his radio debut at the Silverstone British Grand Prix. Out went pedantic and school-masterly Dr Jonathan Palmer, and in came another more successful former F1 racer, Martin Brundle, whose knowledge and incisiveness is matched by brevity and wit.

Walker is determined that Brundle, racing up until the end of last season, should not return to the grids, and described him as a ''real find''.

Detractors argue that Walker maintains a saturation descriptive radio technique on TV, reversing the concept of a picture telling a thousand words.

Walker's infamous mala-propisms, slips of the tongue and high-speed hyperbole are part of the legend, and he puts down any blunders to ''one of the problems of being a human being, none of us is perfect.'' He added: ''If there is a perfect pundit I would not want he or she in the same commentary box thank you.''

Walker avoids preaching only to the converted anoraks ''about how McLaren has stretched its gudgeon pin by one millimetre'' and concentrates on ''entertaining the mass of people''. He believes F1 ringmaster Bernie Ecclestone's high-technology, self-select, multi-channel digital TV service will never be ''gigantic''.

''Obviously I am biased. There is a danger of F1 becoming too analytical. It is a tremendously complex sport and only the total petrol head wants to be his or her own producer, jumping from Villeneuve's roll bar to the Ferrari pits, to the timing screens,'' he argued.

As the ultimate fan, he strives to share that infectious, undiluted enthusiasm without insulting people's intelligence or powers of observation and not patronising with a surfeit of technoblab.

Walker does not share anxiety about lost income from bans on cigarette promotion reducing the sport to penury. When it happens, he believes the flotation of Formula One Holdings will ''bring a cornucopia of riches into the sport'' and the magnetic force to attract alternative blue chip sponsors.

Citing the 90,000 spectator sell-out at Silverstone this year, Walker said: ''It retains an intangible magic. A blend of noise, speed, colour, athleticism, danger and money. ITV brought along a group of their senior professional women to the British Grand Prix and they were besotted. It is a potent mixture. Around 60% of my mail comes from women.''

He also disputes, via experience dating back to a 1930s childhood watching pre-war Auto Unions and Mercedes, the concept of bygone golden Grand Prix ages or halcyon eras. ''Distance lends enchantment,'' said Walker.

How long will he don the headphones and microphone set? ''Don't worry, I will know before anyone else when to quit.'' Gigantic is a high-frequency Walker word. It describes the yawning gap that will be left when he finally switches off the sound link to our homes and hearts.