Last week the City of London trading standards service issued beer mats that can be held against the glass by consumers, to get a rough idea of the quantity of liquid they have been served.
And, if their pint has a deficiency of more than 5%, they can then report to the pub to trading standards.
Harvey said he often sees bar staff tip beer into the drip tray, then top up the glass, to try and meet this percentage – a serious waste of money in the long-run.
According to the BIIAB's and Cask Marque's cellar and dispense training course handbook, wasted beer is one of the biggest impacts on profitability in a pub.
As an example, it states that if one drip tray, per tap per day, is filled with wasted beer due to fobbing, it can equate to more than £16,000 in wasted beer (this is based on a 10-tap account with beer retailing at £3 per pint).
'A shot of gin or whisky'
"Another way of looking at it is this; you can waste the equivalent of a shot of gin or whisky – a 25ml measure – every time you pour beer in the drip tray to correct the size of the head," explained Harvey.
"A 25ml serve in a pint glass doesn't look that much, but it only takes around 24 or those servings to make a pint.
"So if you think about it, if you do that for each pint in every 24 poured, you've lost one pint".
Talking to The Morning Advertiser, Harvey gives his top tips on ensuring that pubs don't pour away profits by trying to get the right head – or get reported to trading standards.
"You need to let it settle, depending what beer it is, and then obviously top it up once it's settled, without losing any beer," he said. "There's a fine line, beer should have a head on it. That's the thing – otherwise it doesn't look like beer, it doesn't smell like beer, it doesn't taste like beer.
"You can still be doing something, you can still do a gin and tonic, or muddling the mojito mint, or just taking the money, or doing the food order, selling a packet of crisps. Just doing the transaction will be time enough, whether it be card or cash, to let it settle."
Fobbing can be caused by anything from a warm cellar to dirty beer lines, warm glass, remote cooler not working properly, beer that hasn't been conditioned properly, or just a poor serving technique.
"I've seen lots of bartenders in London who don't know how to pour a pint, and probably don't know the rules," said Harvey.
'I wouldn't accept that'
"I can stand there in a pub and think 'I wouldn't accept that' but there are tourists or wealthy bankers who don't give a monkey's and can't be bothered the complain. So sometimes the pub does get away with it.
"However, I don't think these beer mats are necessarily fair on the publican, especially the ones that are getting it right. But then again, if they are getting it right, they have nothing to worry about."
Harvey continued: "If the licensee cares, and they actually teach the staff, and they don't suffer fools gladly, this can help with profit through quality.
"So many people say to me 'we have so many staff members that don't know how to pour a pint' - well why are they working in a pub then? Teach them, show them how to do it properly.
"It reflects back to training, and bartenders knowing what is expected of them, and how best to work a bar.
"It is an art. I can sit there watching anyone who knows what they are doing, pouring pints brilliantly for hours, regardless of whether the pub is a high-end or sticky-floor boozer."