Two years ago I was invited to join a Gangmasters Licensing Authority (GLA) raid in Lincolnshire. It was a real eye opener, especially when we came across workers who claimed they were being paid a fraction of the minimum wage for long hours of thankless and physically draining labour.

You try to convince yourself that these are isolated incidents, and in all probability they are, but the shocking revelation this week that children have been found working in English spring onion fields emphasises that the battle is far from over.

The GLA has made huge strides since its inception in stepping up the intensity of its investigations, agreeing a landmark protocol with retailers and vowing to rid the agricultural industry of the sort of abhorrent labour abuse that you would more readily associate with the third world.

Sometimes growers caught by the GLA claim they are unaware of what is going on in their fields. Utter rubbish. Any farmer worth his salt must know if, for example, kids are being employed on his farm.

Yes, margins are tight and I have heard at least one grower blame poor supermarket prices for paying below minimum wage. But much as everyone sympathises, it can’t be an excuse for exploitation.

Now, the GLA is rightly turning its attention to the foodservice sector, an area considerably more fragmented and difficult to police. It’s got its work cut out disentangling the supply chain below the multiple retailer sector, but it is good that it has pledged to adopt the same zero tolerance approach across the board.