Forget the G20 circus. On Saturday afternoon there was a politer protest meeting, in the old railwaymen's club in Oxford. Only a hundred or so people (small children skidding about in the next room too mobile to count) but a microscope is a better diagnostic instrument than a fisheye lens. The theme of the meeting chimed with the wider unease: a huge, arrogant, yet strangely incompetent body was gratuitously messing up ordinary lives. Not a bank this time but Noms, the National Offender Management Service: founded 2004, revamped 2008.

Under government policy of controlling everything from vast distant HQs, run by frazzled people who don't get out much, Noms brought together HM Prison and Probation Services in the name of “coherence” and blethers about a “vibrant mix” of “service-level agreements”. But in effect, in January last year the Prisons element more or less took over the Probation Service, which became a Cinderella.

According to Napo, the probation officers' union, Cinderella must cut its budgets by between 13 and 25 per cent and lose more than 2,000 jobs over three years. The national post of director of probation no longer exists, and in the Ministry of Justice business plan the amount spent at Noms headquarters is, the union claims, as high as the cost of the entire Probation Service for England and Wales. Yet you would think, given government rhetoric, that probation officers would be a priority. What they do is to supervise, mentor and (really quite often) reform the lives of the paroled and criminals on community sentences.

So much for the wider picture. Zoom back in on the Railway Club and the neighbourhood of Mill Street, Oxford. This - where I spend a fair amount of time - is not one of those chic addresses in the leafy North or a modish Jericho. It is a long cul-de-sac, a terrace of brick houses on the edge of the city beyond the railway. These are small homes for young families, new couples and lone pensioners.

Pleasant but not posh. There is one pub, and at the far end a small office block by the river, needing refurbishment. But a week ago Mill Street learnt that the Probation Service is about to sign a lease on this building, extending it into a “mega-centre” of 100 staff, replacing the city office and others in neighbouring towns. Thus every week 350 clients, from petty thieves to violent and sex offenders, would arrive for their interviews or group sessions. That's 70 a day from all over Oxfordshire, walking the long quiet street or approaching by a track through a churchyard and past two nursery schools.

No notice was given: this was a leak. The Probation Service confirmed it when pressed, but coyly refuses to meet residents. City planners are told it is just an office, class B1A under the Town and Country Planning Act, so no change of use is needed. You could argue that by covering “non-resident adult learning” it is actually category D1 - but then, of course, there would have to be democratic public notification, which the Ministry of Justice's agency seems keen to avoid. Mill Street is not amused, though there was shocked laughter when Evan Harris, the local MP, read out the response from Noms: “We doubt the value to the residents of meeting with us before we sign the lease.” Which is a bit like selling the house before mentioning it to your wife.

The protest is not sensationalist or illiberal (indeed, one leading campaigner got so interested in the Probation Service that he plans to volunteer with ex-offenders). It breathes reasonable anger at arrogance, secrecy and a cavalier attitude to citizens' concerns. The local councillor Susanna Pressel, the Lord Mayor of Oxford, confirms that such an office should be in the city centre, near courts and police. Dr Evan Harris concurs, though drily admitting that he has often in his right-on Lib Dem way taken sides against residents' groups (including his own parents) over unpopular but vulnerable groups such as asylum seekers and council tenants. But even he is on Mill Street's side. This is a bum idea: its only merit must be cheapness. For all the mission statements about “focusing on individuals at a local level” it is a secretive and probably false economy of scale.

False? Well, consider the offenders' plight too. A powerful voice at the meeting was Joe, a veteran former prison officer and mental health worker who - not living locally - spent 48 hours worrying whether to stick his head above the parapet. But he did, and is worth hearing. Offenders, he says bluntly, dread having conspicuously to “run the gauntlet” of a quiet street for appointments.

Sex offenders, ordered to keep away from children, will find it difficult to do so up this street. Moreover, Banbury is nearly 30 miles away, Bicester 15, Abingdon a long bus ride. Promises about local needs are oddly served, Joe reckons, by “taking probation officers away from their communities, where in the past they had good relationships with police, even with offenders' families. The work is about building relationships.” Sadly, he predicts many missed appointments: in chaotic or addicted lives a long round trip is not simple. Nor is taking a full day off every week if you're lucky enough to have work.

People will bunk off, and be chucked back into prison for failing to meet probation conditions. How much of a public economy is that, eh?

The whole thing is a bit nuts, reeking of panicky, furtive, distant decisions unrelated to reality. Curiously, it brought to mind the equal nutty waste-through- centralisation I saw when out with the Metropolitan Police for a night of stop-and-search in London. Our vanful of elite officers spent two thirds of its time crawling miles through traffic with the latest felon sulking in the passenger seat, just to find the last vacant cell in a distant mega-station “custody suite”. The police were visibly frustrated. Once there were small local stations, Dock Green-style, with a couple of handy cells each.

But in the past decade more than 650 stations have been closed nationwide. I am told that when you get arrested in Penzance you now score a 45-minute ride to Truro to be locked up. Your mates can continue fighting undisturbed while the cops rack up their carbon footprint.

So there you are. Economies of scale that in the end cost money... managerialist bean-counting from plush London offices... ideas that look good on spreadsheets and lousy on the street. That hour in the Railway Club was, in its way, a more informative snapshot of Britain than all the G20 demonstrations.

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