A judge has warned eastern European criminals that British courts will not be a "soft touch" as he jailed a Romanian gang for a £1m gold robbery campaign.

The 10 gang members came to the UK specifically to commit the crimes and had not done a day's legitimate work while here, the Old Bailey Judge Timothy Pontius said.

He gave them sentences totalling 82 years and 10 months despite the fact that they pleaded guilty and had no previous convictions. They were also told they would be deported after serving their sentences.

The judge said the gang had entered the UK as EU citizens with the intention of robbing jewellery shops of large amounts of high-quality gold. Only a fraction of their haul had been recovered from the six raids or attempted raids – leaving the robbers with £1m.

Pontius said: "None of the defendants appear to have done an honest day's work while they were here. All will be deported, and rightly so."

He said there were fears that an influx of people from Romania and Bulgaria when restrictions are lifted next year would lead to an increase in crime. He warned: "Anyone who comes to the UK, irrespective of whatever part of the world, wanting to commit serious crime must clearly understand such abuse of the hospitality of this country and its people must be seriously punished.

"It follows that the more grave the crime, the more severe the retribution will be. No one should think for a moment that courts in the UK will be a soft touch. Sentences such as these must be a powerful deterrent not only to homegrown but imported criminals."

The gang carried out seven raids in six months, emptying display cabinets and fleeing in minutes before police could respond to alarms. They were caught after officers kept watch on a makeshift campsite they were using on waste ground near the A12 in Essex. After being arrested, Ovidiu Gabor, 25, told police: "I don't care, I go to prison to go on holiday."

The gang pleaded guilty to conspiracy to rob.

Jonathan Polnay, prosecuting, said: "This was a sophisticated, well-planned conspiracy deliberately targeting jewellers. All the defendants are Romanian. These are all relatively young men who came to this country to rob."

They targeted Asian and Turkish jewellers where there was a large quantity of high-carat gold that could be melted down and sold. The usual plan involved one of the gang, dressed in pinstripes and a trilby, being buzzed in and holding the door for an accomplice to smash his way in with a sledgehammer. The rest of the gang would then run in and smash display cabinets with bats and hammers before fleeing with jewellery. They would make off over railway lines, discarding their weapons and outer clothing.

The gang netted more than £1.1m last year but only £135,580 has been recovered. In March last year, £500,000 of goods was taken from a shop in Wembley, north London, which was "trashed". Nothing was recovered.

A month later, part of a £248,648 haul was found in a hole the gang had dug to hide evidence near a shop in Ilford, east London, said Polnay. In August, £341,435 of goods was taken from a shop in East Ham, east London.

Two other attempted robberies were abandoned and the gang were captured after being caught red-handed during a £62,580 robbery in Turnpike Lane, north London, in September. An elderly man was injured when he was struck with a hammer before Flying Squad officers made arrests using Taser guns.