It was a cheap Chinese restaurant, just near the bus terminal in a quiet Northern town. Now, I’m partial to Chinese food when away on business, not least because the single male traveller can usually eat a plate of chow mien or special fried rice without feeling awkward and without being tempted by the demon drink.

The place in the bus station was pretty basic - the tea was builders’ rather than jasmine, an industrial-grade teabag floating in a navy blue mug - but it was a wet Sunday evening and I was hungry. It would do.

Time to pay. I asked for a till receipt. “No,” I was told, firmly.

“Word on the street is that the UK political class is on the make to an extent that hums of corruption”

I looked up, surprised by the bluntness. The owner half-smiled: “But I can write one out for you if you like. How much shall I make it out for?”

It was a revealing moment. The next day I’d be starting an investigation at the local hospital that partially revolved around questionable expense claims. In a town and a culture where low level financial mischief was clearly not unusual, exactly how much reliance should I place on all those carefully presented receipts?

After a while, if you travel for work, asking for a receipt becomes a reflex. Whether in a station, a taxi or a restaurant, one collects the valuable vouchers which smooth the route to reimbursement. The ritual is not unique to the public sector. Journalists have a long and proud tradition of imaginative expense claims. Any organisation big enough to have a finance department will have a process whereby monthly claims, supported by receipts, are countersigned by a manager and scrutinised by clerks prior to payment. It will have allowances and limits. And it will no doubt also have one or two employees adept at exploiting the system

It’s a tradition riddled with perverse incentives. Here are just a few:

Live or work in London? You almost certainly own an Oyster card. However, if you use your Oyster card for a £1 bus journey, you’ll have no receipt. So buy a travelcard instead! Yes, at £5.60 it’s a little more expensive, but you should have no difficulty with your claim and will be able to travel for free in the evening.

Travelling by train? You could save pots of money by buying an advance-purchase ticket. Even first class travel is cheaper this way. But this will tie you to specific trains, causing untold grief if your business is rescheduled; and first class is a complete no-no. So buy a full-fare walk-up ticket instead. As long as it’s standard class, the claim will go through unchallenged.

Usually drive? Go by train, buy whatever ticket you fancy and claim the car mileage instead. At 40p a mile you should be able to trouser a few quid.

Staying away overnight? You’d really like to visit some old friends, stay in their spare room, and take them out for a curry or a pizza and a few beers to show your appreciation. But how would the finance department treat the receipts? Booze? On expenses? So book that £90 hotel room, and blow another £20 on a mediocre room service meal. That’s what business travellers are supposed to do, isn’t it?

The boundary between what constitutes an outright expense fiddle and what’s merely a little flexibility in the rules is not always clear, as MPs with innovative second home arrangements or a liberal approach to employing their own family members have come to realise. Bulking that Chinese bill up to £25 and pocketing the difference would be fraud, as would accepting a blank receipt from a taxi driver and writing in the amount of one’s choice. But how about that old one of travelling first class “so I can work”? Or, at the extreme, the extensive and expensive foreign travel, dining and hospitality record of the former head of the National Audit Office?

The significance of all this for NHS leaders lies in Sir Christopher Kelly’s inquiry into MPs’ expenses and its ramifications for the public sector at large. Around a million expense claims covering the last four years are to be published. Shame and scandal are inevitable; some even suggest there may be suicides, for expense claims reveal much about a person’s way of life and habits. When even a £10 “adult” film viewed at a hotel hits the front pages, who knows what might emerge this summer.

If the substantive issue of the review is MPs’ second home allowance, the underlying theme is no less than restoring confidence in standards of behaviour in public life. Word on the street - and in the press - is that the UK political class, like the banking establishment, is on the make, and to an extent that hums of corruption.

There is little doubt that transparency around expenses claims will be at the core of whatever system finally emerges for MPs. All claims and receipts will be published and open to public scrutiny. The press will take a keen interest.

Do you seriously suppose, gentle reader, that the same transparency and scrutiny will not quickly extend to the doings of NHS managers, senior and not so senior: the profligate bureaucrats of popular mythology? Expect headlines with words like “lavish”, “junket”, “luxury” and “on expenses”. Expect embarrassment.

It is often easy to persuade oneself that an expense is justifiable, on the “because I’m worth it” principle: harder to defend that later when a hostile press comes calling. And in a climate of public spending cuts, shaming managers might even be a convenient way of redirecting the spotlight.