The fate of thousands of British museums is determined by a select group of well-heeled, well-connected men and women

"So, exactly how many visitors do you get?" asks Admiral Sir John Kerr of Patricia Osborne, chair of the trustees of the Cowper and Newton Museum, Olney, Bucks. "3,000." "Ah, that'll be 3,000 a..." "A year," says Mrs Osborne without embarrassment, "but we have great plans to increase this to 15,000."

Sir John Kerr tries to imagine 15,000 people a year trampling up the narrow stairs of one of the country's smaller and less well-endowed museums. Sir John likes to ask this sort of question and to ponder the ramifications of the answers. As a former commander-in-chief Naval Home Command, Sir John is something of an expert on logistics. Which is why from this year he is chairman of the Audit Committee of Lancaster University and one of the commissioners of the Museums & Galleries Commission (MGC). It is in this latter capacity that Sir John is marching around the Cowper and Newton Museum, in company with fellow commissioners.

Sir John and crew sail in stately fashion along creaking floorboards, asking pertinent questions, making helpful suggestions and generally lending a sympathetic ear. They are part of a national body of the influential and the good who keep a weather eye on Britain's museums from Camber Sands to Cape Wrath. This is the third local museum they have visited over the past two days as part of their regular round-up of the nation's total of 2,000.

"Commissioners make two visits a year to selected parts of the UK," says Timothy Mason, director of the MGC. "These tours provide a good opportunity to find out what is happening on the ground and to meet museum staff together with members of museum governing bodies and representatives."

The MGC is the government's official adviser on museum policy in the UK and its 15 unpaid members chaired by the avuncular Graham Greene, a Trustee of the British Museum and former chairman of a number of publishing companies including Chatto, Bodley Head and Jonathan Cape, are appointed by the Prime Minister.

"Museums are a very serious part of our economy as well as our culture," says Mr Greene, "so the politicians can't afford to ignore them even if they wanted to. Of course, they also find it a relief to talk about the acquisition of a Titian for the nation after a round of heavy talks on interest rates and unemployment."

Unpaid, hard-working and wearing their combined learning behind a gentle and almost self-deprecating manner, the commissioners of the MGC are, it must be said, a delight to spend an afternoon with and the least frightening "inspectors" imaginable. They can, however, help make or break museums, proffer grants and, today, guide hungry curators in the direction of Lottery funding through either the Millennium Commission or the National Heritage Memorial Fund.

Kindly they may be. But the gang of 15 do not miss a trick. Between them, they have covered many senior jobs in industry, the arts and museums. Eagle-eyed Dame Margaret Weston, an electrical engineer by training, was director of the Science Museum from 1973-86. She is a trustee of the Fleet Air Army Museum, Yeovil and a proactive chairman of the Horniman Museum and Public Garden Trust.

Alan Warhurst was director of the Manchester Museum from 1977-93 and driving spirit behind the MGC's initiative to register all Britain's museums so that they can meet and maintain certain standards.

The Baroness Brigstocke was High Mistress of St Paul's Girls' School from 1974-89 and was Governor of the Royal Ballet School during much of the same period. If central school of casting was to pick a grand headmistress, Baroness Brigstocke would fit the bill perfectly. Today, she listens to curators' problems much as she must have lent an ear to teachers and Paulinas some years ago.

The list goes on, impressively so, but that is enough for now, as we troop up the stairs of the Cowper and Newton Museum, Olney.

The museum is, as Sir John Kerr might be inclined to say, rather a rum affair. Ostensibly, this rambling pair of stone cottages fronted with a unifying and grand brick facade (1740s) is dedicated to preserving the memory of the poet Cowper and the former slavetrader-turned-clergyman Newton. It was in the summer house (or perhaps the greenhouse) in the walled garden of this odd house that rather forgotten poems like "John Gilpin" and stirring hymns like "Amazing Grace" were penned. Cowper (pronounced Cooper, say half the staff; the others plump for Cowper) and Newton were obsessive penpals, but they are little known today outside the confines of Olney.

So, as if to widen its appeal, the museum has built up a collection of dinosaur bones, excavated locally, and locally made lace. A team room will open soon, staffed by unpaid volunteers.

A Victorian kitchen superintended by a pouting blonde mannequin (masqerading as a lacemaker) has been installed, not because Cowper and Newton (Georgians both) cooked their suppers in a Victorian kitchen, but because the trustees thought it an interesting addition.

The commissioners sip tea and hum and hah politely. They are jolly tactful. "Oh, we have to be very tactful," says Mr Greene. "We see many museums like the Cowper and Newton. They are getting on a bit [the Cowper and Newton is about to celebrate its centenary] and sometimes have got a little confused or rather lost their way. But, the enthusiasm of those who give their time to run them is infectious. Our aim is to help them in every way we can."

"Perhaps they could put the dinosaur bones in a garden pavilion," says Margaret Weston. "That way they could have their cake and eat it while maintaining the integrity of the museum's original purpose."

"But a lot comes down to money," says the Marchioness of Angelsey as we get back on the coach and head back to a reception at Chicheley Hall, a glorious Baroque pile where the commissioners have been staying overnight. "There are 2,000 museums, many of them rather poor. Sometimes a tiny sum of money makes all the difference. Just think of the revenue of the Cowper and Newton."

I think. Three thousand times pounds 1.50 equals pounds 4,500.

"Yesterday," says Jack Baer, former chairman of Hazlitt, Gooden & Fox, and an expert in acquiring works of art for museums in lieu of tax and duty. "we visited Waddeson Manor, the Rothschilds' Victorian mansion. They've just had a new lighting system installed to light the paintings. Extraordinarily good. But, then you see, the Rothschilds are not exactly short of a penny. So we do get to see the extremes."

The museums themselves are grateful for the attention paid them by the MGC. "Two-thirds of British museums," says Alan Warhurst, "are now registered with the MGC. We can offer expertise in many areas, not least security measures and how to get artworks in lieu of death duties.

"Most museums aspire to join us because of the practical help we can give them and the ways in which we can introduce them to all sorts of people who might be able to help."

Local politicians, as well as curators, know that the MGC can make connections in high places that they would be unlikely to make themselves. So, naturally, they turn out in force on the stroke of six at Chicheley Hall for a reception. Wine and canapes are served in the grand entrance hall.

"They've had a bit of a problem with the ceiling," says Admiral Kerr. So they have. Designed by William Kent and a bit of a museum piece itself, the ceiling collapsed after a guest left a bath running.

Under the drooping Kent ceiling, flesh is pressed, wine quaffed and introductions made. Everyone has high praise for the revamped Buckinghamshire County Museum in the mutilated centre of nearby Aylesbury and high hopes that the Museum of Industry and Rural Life, Wolverton will get a bit of a nourishment from the weighty Millennium pot.

Tomorrow, there is another closed-doors MGC meeting (09.15-12.30), lunch at Chicheley Hall (12.30-13.30) under another grand ceiling, visits to the Natural History Museum, Tring (14.15) and the Walter Rothschild Zoological Museum, tea and biscuits (16.00) and the train from Tring back to London (arr Euston 17.34).

The MGC commissioners, unpaid, hard-pressed, individualistic and enthusiastic come across as just the sort of body to which one can trust the development of our small and local museums. Between them they have no axe to grind, no hidden paymaster and have got to the stage in life (some older, some younger) when they are past the stage or need for political manoeuvring.

Of course, the big question remains unanswerable (at least by MGC commissioners): how many more museums do we need? "Now, there you've stumped me," says Admiral Kerr, still thinking about how 15,000 goes into the Cowper and Newton Museum, Olney, Bucks.