I'm usually reluctant to give the opposition the oxygen of publicity, but this week Time Out's comedy section has done a nice round-up of the Edinburgh Fringe's work-in-progress shows coming up in London. I'd been working on a similar piece myself to launch BTJ's new Preview Section and will be posting Preview of the Day tweets to highlight the shows you really must see

Edinburgh previews in London in June and July come around every year but still seem to persist in being one of comedy's best kept secrets. It feels as if most comedy goers would rather play safe and go to a regular club such as the Comedy Store when they could try out something completely new. Work-in-prorgress shows are great for a number of reasons.

1) They are cheap. Daniel Kitson's £3 previews of his tour at the Hob in Forest Hill earlier this year must have been the steal of the century. The Hob has more juicy previews coming up – see here.

2) You get to see great performers before the Edinburgh Fringe hype, so you can get a head start on your friends and claim bragger's rights at the watercooler.

3) You may even see a future Foster's Comedy Award winner that will sell out, be the talk of Edinburgh and carried around on a sedan chair and then be more expensive when they come back to London in the autumn (did I mention that previews are super-cheap and sometimes even free?  The Invisible Dot in King's Cross has recently been doing free shows and while their previews do cost £10 for that you get two sets and a gratis BBQ between them. What's not to like?

4) You get to see stars up close. and I mean real close. No setting the alarm for 8.59am to bag front row seats at the Hammersmith Apollo, just pitch up at Comedy De Luxe in Spitalfields on Tuesdays (run by Chortle – who says BTJ doesn't help its rivals?), hand over £7 and make your way to the front to get turned on to social justice by Mark Thomas, ranted at by Tony Law or simple terrified by human dynamo Phil Nichol.

5) A bad preview is perversely funny anyway. They might not be perfect but I rather like the fumbling of notes and the way that some jokes prompt tumbleweed to drift across the stage. It's the test of a real pro that they can die on their arse in London in July and triumph in Edinburgh in August. However...

6)...A good preview can create a buzz. I remember Humphrey Ker generating a buzz before he went up to Scotland and picked up a Best Newcomer Award for Dymock Watson! Nazi Smasher. I don't want to put any pressure on him, but I've already been hearing nothing but good things about Colin Hoult, who is on at the Invisible Dot this Wednesday in a double header with Claudia O'Doherty.

OK, thats's the upside, so is there a downside to these road-test gigs? Well, one of them is the fact that people don't seem to want to go to them so the atmosphere can be supportive but a little bit flat occasionally. The only way you can really prepare for the Edinburgh Fringe is by doing as many previews as possible and honing, honing, honing. Yet I've been to gigs that have been a whisker away from being cancelled due to small turn-outs. Sometimes the only people in the audience have been the promoter, me and a couple friends. And yet the comedian really needs to do their show. It is the only true way of finding out if any of those scribbles really work. In fact it is the only real way of finding out if the show lasts the requisite 55- 60 minutes. It is all very well doing it in front of your mirror but if it takes 55 minutes at home watched by your cat and you don't take it to a club in advance you might get to Edinburgh, do your first preview and find that with the adrenaline pumping through your veins you get through it in 30 minutes. Particularly if there are no laughs.

So comedians who know what they are doing do previews. Which is why you can see the likes of Claudia O'Doherty and David Baddiel around town over the next few weeks. And we also get some special guests getting acclimatised here too. if you are not from the UK a London preview is a good way of getting to know what a UK audience likes. Maybe Judah Friedlander should have done a few warm-ups before inviting the press to his London debut. Cult Canadian comic, Baconface (pictured), who has been championed by Stewart Lee, is currently preparing for his Edinburgh debut with a no-reviews-please warm-up run at the Soho Theatre. So get down to these gigs or miss out on seeing possible comedy royalty at a Poundland price.