So you need some building work done. Lots of people do. And for a variety of different reasons. You might want an extension to your home, such as a conservatory, an extension to your kitchen so that it becomes bigger and you can entertain friends and family there, which many people do today.

You might have a growing family. Little did you know that they all want their own bedrooms, even if there are only two of them, and so you need to make an extra room in the basement or the loft. You might need to do the same thing if you have to take in and look after an ageing relative.

Perhaps you need a garden wall replaced because it is crumbling and falling down. Maybe you want to convert a garage into an office: many people who are starting to work from home these days need somewhere to use as an office in order to get away from the kids.  Working from home on the internet is fine, but you still need peace and quiet.

For any or all of these reasons, and no doubt dozens more, you need a builder. The problem is: where and how do you find the best builders in London? There are thousands of builders in London and they all claim to be the best. Every last one of them. You don’t need an IQ of 165 to work that out. But how do you KNOW?

At all costs, you need to avoid cowboy builders, and there are plenty of those about. The point is that anybody – you or I included – can claim to be a builder. However, just because you once built a garden wall which didn’t actually fall down doesn’t necessarily make you a builder. You watched a couple of videos on YouTube and decided to have a go.

Probably the best way to begin your search is to understand the things that you should look out for which indicate that the builder you are talking to is not actually the best for you. A builder who asks for cash up front should be instantly rejected. You should only ever pay a deposit to cover the cost of materials and then agreed payments in stages as the work progresses, and you should get that agreement in writing.

If the builder is in a hurry to start the work, it is probably because he has no other jobs on and needs the money. Beware.

He gives you a quote that is dirt cheap. Either he is employing rubbish labour or using rubbish materials. Or both.

He is not registered for VAT. That means he is turning over less than £85,000 a year. Either that, or he is deliberately avoiding registering. A builder turning over less than £85,000 a year is, in fact, doing very little work when you take into account the cost of materials, and if he is avoiding registration that tells you everything you need to know.

The builder cannot provide you with any references. You should ALWAYS ask for references and preferably talk to the persons who gave them.

He refuses to provide you with a timescale for the work. "It takes as long as it takes" is not good enough. Any professional will be able to give you a reasonable estimate. 

The builder won’t offer you a written guarantee. That says it all.

So what DO you look for in the best London builders? Well, the foregoing should give you some guide. You should ask for references and check them out. You should also find out which trade body the builder belongs to - the Federation of Master Builders, the Guild of Builders and Contractors, or the National Federation of Builders. Check whether he uses sub-contractors – which many do – and ask what insurance he has if something goes amiss.

Always ask for a written quote, and also ask how long that quote is valid for. You should also have a written contract which agrees the stages of work and also the stage payments, signed by both parties. In addition, you should have a council inspector check that the work meets building regulations and you should also retain the final payment until any snags have been rectified.