I can only ever review what I see. I can't review intent, and I can't review the fact that the people putting on the show will almost certainly have expended much time and effort, and may even have mortgaged someone's granny's house to raise the money.

So where does that leave the critic – and indeed the audience – when it comes to community or participatory theatre, where often the performance is but the tip of the iceberg? The show, which may last just a few hours or a day or so, is merely the visible manifestation of a much longer process that has been taking place over many weeks, maybe even years. Should you review the tip you see any differently from the way you would another project, and should the audience be expected to make allowances and respond differently because it is a participatory project?

I've been thinking about this since I saw National Theatre Wales's De Gabay in Butetown in Cardiff recently, which was the recipient of a £175,000 award from the Calouste Gulbenkian Foundation to create community projects in disadvantaged communities. It's perfectly possible that the work that went on in the community was excellent, but it certainly didn't translate into the performance. You can read some responses here and also here.

It is, of course, perfectly possible to have a terrible process and still deliver a great show, but I suspect if the public performance doesn't come off, the process may be open to question too.

Community theatre has been around for many years – on 9 March the London Bubble theatre company marked 40 years of working in participatory arts with a seminar, but it is something that we will see a great deal more of in the coming years as theatres and companies rightly realise that they have a significant role to play in making meaningful connections with communities. We've already seen some extraordinary work, including NTW's The Passion and shows such as Wildworks' The Beautiful Journey.

But there have also been plenty of shows that fall into the De Gabay category: they may have served a useful purpose in the community, but nevertheless evolved into miserable audience experiences. There seems to be so much of this sort of work being created that I wonder whether what is being learned over different projects is really being shared. Companies undertaking such work need to learn from one another's mistakes and successes.

In the end, if the project has a theatrical manifestation – if an audience is invited and critics too – then it has to be judged on the basis of the performance. To take any other approach is to patronise all those who have participated in its making, whether they are professional or community participants. Audiences don't want to leave saying: "Oh that was great – for a community show." We want to leave filled with delight and enthusiasm, having witnessed a great piece of theatre.