A flagship of the pro-Brexit flotilla that sailed up the Thames was involved in the UK’s largest ever frauds involving illegal catches of fish, it has emerged.

The Christina S, a 72-metre-long pelagic trawler, was one of two largest vessels to take part in the river protest organised by Scottish skippers heading to Westminster to call for the UK’s withdrawal from the EU.

But in 2012, skipper of the boat Ernest Simpson, 65, and his son Allan, 43, were fined £65,000 each illegally landed mackerel and herring worth a total of £2,031,501. The pair also had to pay "proceeds of crime" confiscation orders of over £360,000.

The pair were caught after a seven-year investigation prompted by suspicions that large profits in the fishing industry could not have been made legally given EU fishing quotas at the time.

Judge Lord Turnbull, who presided over the case, branded it an "episode of shame" for the industry.

Lindsey Miller, head of the Serious and Organised Crime Division, said: "These individuals had no regard for the law or for the consequences such large-scale under-declarations would have on fish stocks, the environment or the hard working fishermen trying to make an honest living in the industry.

"There is no place in Scotland for those who want a lifestyle funded by crime."

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The Christina S now owned by Peter and J Johnstone a company controlled by major fishing firm Andrew Marr International, which controls 12 per cent of all UK fishing subsidies through a series of subsidiary companies, according to Greenpeace.

The 2016 Sunday Times Rich List said Andrew Marr and his family are worth £122m - making them the 825th richest family in the UK.

Andrew Marr International had a stake in the Christina S between 2005 – 2008 when the so called ‘black fish’ scam took place, but they were not among the firms prosecuted and there is no suggestion they or the vessel's other owners played any role in the scam of faced prosecution.

The flotilla, which was joined by Ukip leader Nigel Farage, was supposed to represent British fishers struggling under unfair EU rules depriving them of their fair share of fishing rights.

But Greenpeace executive director John Sauven said it was an unfortunate choice of vessel to lead the flotilla.

"A trawler once involved in Britain's biggest fishing fraud and now owned by a Sunday Times Rich List millionaire is an unfortunate choice to lead a flotilla supposed to represent a fishing industry on its last leg because of Brussels,” he said.

“It's also an unwitting clue to where the real problem lies. It's not the EU but the grossly unfair division of fish quota rubber stamped by successive UK governments that's threatening the livelihoods of thousands of small-scale fishers.

“Brexit cheerleaders like Nigel Farage are cynically exploiting the legitimate anger of many British fishermen for political gain.

“Quitting the EU will only condemn the industry to years of wrangling over new fisheries agreements, with no guarantee of a better deal for fishers or stronger protections for our seas."