They always look so appetising and so Christmassy, those stalks of fresh Brussels sprouts dominating the supermarket vegetable shelves. There they are among the carrots, parsnips, swedes and other seasonal vegetables.

You can picture them being harvested in the snow-flecked fields of Fenland by apple-cheeked happy farm workers humming carols as they pick the sprouts on a crisp frosty morning.

Why, it could be a Christmas card image or a shot from the latest BBC documentary recreating the halcyon days of historic farming.

In fact the reality is not quite so wholesome. Modern day vegetable growing and picking is indeed often Victorian but not in a pretty sepia Christmas card way.

Most vegetables are picked by gangs of mainly immigrant, poorly paid workers controlled by licenced gangmasters. They are often among the worst paid and treated of any workers in the land.

Just how bad it can be was revealed in a court case this month in Norwich that saw Lithuanian gangmaster Audrius Morkunas jailed for seven years.

It was the first ever prison sentence for acting as an unlicensed gangmaster. It was just the tip of the iceberg in an industry heavy with abuse and corruption.

Morkunas had organised gangs of fellow Lithuanians as vegetable pickers, vegetable and chicken food processors in the food industry.

He charged workers £400 each to find them criminally underpaid jobs and also rented them crowded and unsuitable accommodation at an exorbitant rent. Some paid £50 a week to share a bed. He also charged each worker £5 per day for the transport he provided.

Morkunas used violence to control many of the workers. The assault charge resulted from him beating a worker with an iron bar - a crime that was captured on CCTV.

He also controlled the bank accounts that workers opened, as well as taking control of many of their identity documents, including passports and driving licences. The workers invariably built up a debt to Morkunas that he used to exploit and control them.

This gangmaster it seems was also a gangster who had built up an organised crime organisation. As so often these immigrant workers had no trade union to defend their rights. Many were virtually slave labourers.

The gangmaster was also found guilty of causing actual bodily harm and possession of an offensive weapon. He and three henchmen, some of whom also had weapons, carried out a targeted attack on one man entrapped in this criminal web.

The victim had dared to refuse to pay the money demanded for finding work and accommodation.

The court heard that Morkunas exploited at least 250 people and his income had amounted to at least £100,000.

Morkunas operated around Norfolk using a garage he ran in Duke Street, Norwich, as a base.

Detective Constable Neil Starland, from Norfolk Constabulary's economic crime unit, said he hoped the sentence would send out a strong message to others involved in this type of illegal activity.

The court heard that if the workers did not comply Morkunas and his gang would use force. The workers were trapped, slaves in an alien environment.

Members of the Morkunas gang, Kestutis Petravicius and Eridas Daugintis also received custodial sentences.

The case is the first in which an illegal gangmaster has been brought to justice under new regulations. There are hundreds of gangmasters, many of dubious reputation, organising seasonal work in British agriculture.

John Steinbeck wrote eloquently about the plight of immigrant workers slaving in the fields of California in the 1930s.

Today it seems those same Grapes of Wrath are growing in the fens of north Norfolk.

Meanwhile the big supermarkets are, as always, more concerned about the prices they pay for their vegetables than the ethics of the industry that grows them.