By Brian Wheeler
BBC News political reporter
With public lavatories fast disappearing from Britain's High Streets, spending a penny is not as simple as it used to be.
Britain's public toilets are rapidly going down the pan
All too often it involves a cringe-making visit to a pub or a cafe with a big sign outside saying toilets are for customer use only.
"Everybody knows you kind of sneak in, sidle in, looking around and make a beeline for them, hoping nobody will say 'Oi, what do you think you are doing?' as you go in," says Labour MP Phyllis Starkey.
It is even worse when you have children, she adds.
"Any mothers of young children know that even if you go to the loo before you leave there is always one child who wants to go as soon as you get to the playground."
But it does not have to be like this.
In Richmond, south-west London, pubs, restaurants and supermarkets are paid £600 a year to open their facilities to non-customers.
The borough used to be like many other parts of the UK; its public lavatories were difficult to find and - in the words of one council officer - in a pretty "horrible" condition.
But the public has access to 75 clean, well-maintained loos in prime locations around the borough, thanks to its Community Toilet Scheme.
The facilities are clearly labelled with a badge in the window and some are even signposted from the street.
The scheme costs less than keeping the old public conveniences open - or replacing the widely disliked automated ones that used to litter the borough.
Just 3% of local people ever used these Tardis-like contraptions, the council says, which added up to "£8 per pee".
On Tuesday, Ms Starkey toured some of Richmond's community loos with MPs from the communities and local government select committee, to find out how the scheme works.
"The big issue is that upgrading existing facilities or building new ones is very expensive and it's not a legal obligation on councillors to provide public conveniences, so if they are economising this is one of the areas in which they economise, regardless of political control and this community toilet is a lot better value for money.
Phyllis Starkey is on a mission to solve Britain's loo shortage
"You get a lot more loos, more widely spread, and of course, they are all overseen because they are in businesses where there are people who are running the business.
"The council needs to do more work in informing its residents so that they know what the badge means and I guess if you were someone from outside the area you wouldn't necessarily."
Frank Dupree, landlord of The Cabbage Patch pub - one of the venues on the MPs' itinerary - says it is a "win-win" situation.
"From the council's point of view, this scheme is less than what they used to spend on pretty grotty public toilets. From our point of view, we get a fee and we get a possibility of extra customers."
He says families with children are welcome to use the facilities and he has even installed nappy-changing facilities.
The local branch of Waitrose says it is also happy to take part in a scheme which benefits the local community - although the supermarket says it spends more than the council grant on extra toilet rolls and new facilities.
A small number of businesses have turned down a request to join the scheme - and there is concern about its viability in areas which attract a lot of visitors. Richmond council sets up temporary toilets when there is a rugby match at Twickenham.
But the council says at least 100 other boroughs have expressed interest in following its community toilet idea and a number have already set up such a scheme.
And with cash for new public toilets likely to be thin on the ground, the select committee is likely to recommend extending the scheme even further when it reports later in the year.
It has already changed one aspect of pub culture forever, according to Frank Dupree.
"We've all done it - ducked into a pub, thinking will anyone notice me? And we don't get that any more. People can walk in, bold as brass and help themselves."