An army sergeant has been given a life sentence with a minimum term of 18 years after being found guilty of trying to murder his wife by tampering with her parachute before a skydive so he could begin a life with a secret lover and use a life insurance payout to clear his debts.

Emile Cilliers, 38, arranged the jump as a treat for his wife, Victoria, soon after the birth of their second child, but he removed vital components from her parachute, causing her to fall 4,000ft (1,200 metres). Victoria, a physiotherapist, survived after landing in a soft, ploughed field but was seriously injured.

A jury at Winchester crown court found Cilliers guilty of two counts of attempted murder, one related to the jump, and the other to his tampering with a gas fitting at the couple’s home in Amesbury, Wiltshire, a week before the jump to try to cause an explosion while he was at work. He was also convicted on a criminal damage charge.

In a round of television and newspaper interviews after the verdicts, Victoria Cilliers said she still could not see her husband as a killer and was controlling her emotions for the sake of their two children.

She told ITV: “I’ve been though every emotion under the sun. I’ve had plenty of time to think about things, which is probably why I’m not overtly angry, partly because I’m still in shock, slightly stunned about the whole thing. Also, I’ve got two young children. I’m the sole carer for them. I can’t be angry, bitter, really emotional. I need to keep an even keel for them.”

She said she had spent the past three years telling her children their father had gone away for work, revealed she had no plans for divorce and intended to visit Cilliers in prison to confront him about what happened.

A police investigation was launched after it was discovered that pieces of kit called “slinks”, which connect the canopy to the harness, had been removed from the parachute rig.

Detectives found that Cilliers, who has six children in total, was having affairs with two women and had discussed beginning a new life with one of them. He had also been in contact with sex workers, had heavy debts, was being chased by loan companies and increased an insurance policy so he would benefit if his wife died.

Cilliers, of the Royal Army Physical Training Corps, told Winchester crown court that a “random killer” may have sabotaged his 42-year-old wife’s rig at the Army Parachute Association at Netheravon, Wiltshire, on 5 April 2015. He also suggested the jury needed to consider whether she had tampered with her own parachute because she wanted to kill herself.

After the convictions, DI Paul Franklin, who led the case, said: “Emile Cilliers has shown nothing but contempt for his wife. On two separate occasions he made serious attempts to murder Victoria. He has failed to accept any responsibility for his actions, which reinforces our view that he is a cold, calculating and callous man whose only duty of care is to himself.”