Military memorabilia hunters sparked a major environmental alert when they dumped Second World War mustard gas canisters in a Lincolnshire lake, a court heard.
The trio discovered the lethal canisters in an old store building while searching the site of a former military base at Roughton Woods, near Woodhall Spa, looking for items.
They removed 16 of the canisters and emptied three of them onto the ground.
Nottingham Crown Court heard that initially the trio were not sure what the canisters contained, but after seeking advice from fellow military enthusiast Paul Spence it was identified as mustard gas and they were told “leave them alone and never go back there”.
They were advised either to dig a hole and bury the canisters or call out the explosives ordnance disposal team.
Instead they dumped the canisters in Stixwould Lake which is part of the local watercourse and resulted in the potential devastation of waterways in the area.
The matter only came to light a few days later when Martyn Tasker sought hospital treatment for blisters on his arm.
The following day his wife Michaela collapsed while waiting to see her doctor for a respiratory problem which was linked to her exposure to the chemicals.
Police became involved but initially they did not reveal they had dumped the canisters in the lake.
The subsequent investigation led to a £300,000 clean-up operation involving 20 different agencies after police declared a major incident. A total of 150 mustard gas canisters were found on the site.
Specialists from Porton Down were brought in by the Ministry of Defence and the entire area was sealed off for a fortnight.
As part of their investigation police later searched the home of Martyn Tasker and discovered two Bren light machine guns under a bed. 10 rounds of ammunition were found in a bedside cabinet.
Martyn Tasker, 40, his wife Michaela Tasker, 32, both of Longdales Road, Lincoln, and Stuart Holmes, 51, of Witham Road, Woodhall Spa, each admitted breach of the Chemical Weapons Act by possessing mustard gas canisters between September 27 and October 1 2017.
The three also admitted breaching environmental protection laws by causing the discharge of mustard gas into Stixwould Lake near Woodhall Spa, on September 30 2017.
Holmes further admitted disposing of mustard gas in a manner likely to cause pollution to the environment or harm to public health between September 28 and October 1 2017.
In addition Martyn Tasker admitted two charges of possession of a Bren light machine gun and a further charge of possession of 10 rounds of ammunition without a firearms certificate on October 4 2017.
Martyn Tasker, described by the judge as the prime mover, was today jailed for five years. Michaela Tasker and Stuart Holmes were each given a 12 month jail sentence suspended for two years.
Mr Justice Jeremy Baker, passing sentence, told them “The potential of harm from the mustard gas was of a very high order.
“Paul Spence told you to either dig a hole or call the explosives ordnance disposal team because it was not worth risking your lives. The three of you decided to do otherwise.
“With your knowledge of the extremely hazardous nature of the contents of the canisters I am satisfied that the decision to dispose of the canisters in this manner was designed to cover up the fact that the three of you were in unlawful possession of them.”
The judge added that the machine guns were both capable of being fired and were held in an insecure place. He added “They could so easily have fallen into the hands of organised crime.”