An army sergeant who was having affairs with two women attempted to murder his wife by tampering with her parachute before a skydive he had organised as a “treat”, a jury has been told.

Emile Cilliers is accused of deliberately removing vital components from a parachute rig, which led to his wife, Victoria, plunging 1,200 metres (4,000ft) to the ground during her jump in Wiltshire.

Winchester crown court heard that Victoria Cilliers, a former army officer and highly experienced parachutist, spiralled to the ground but “miraculously” survived the fall.

The jury heard that a week before the incident at the army parachute association camp at Netheravon, Salisbury Plain, Cilliers, 37, allegedly tried to kill his wife, 40, by interfering with a gas pipe at their home, hoping to cause an explosion when she lit the stove.

It is claimed that Cilliers was having an affair with a woman he had met via the dating app Tinder and had vowed to begin a new life with her. But he was also having a sexual relationship with his former wife, Carly Cilliers, the court heard.

Opening the prosecution case, Michael Bowes QC said Cilliers had shown callousness and contempt towards his wife, a physiotherapist working with the British army.

He said Cilliers, of the Royal Army Physical Training Corps, had debts of £22,000 and he believed he would be set to receive a £120,000 insurance payout on his wife’s death.

Cilliers denies two counts of attempted murder.

On the day of the jump – Sunday 5 April 2015 – the skies were cloudy and Victoria Cilliers, who had taken part in 2,600 jumps before, thought about going home. But Cilliers told her: “It will be worth it eventually.” The weather improved enough for a “hop and pop” from a medium altitude, in which jumpers must open their parachutes as soon as they leave the plane.

Victoria Cilliers was the last to jump. “Straight away she realised something was not right,” said Bowes. She cut away her main parachute and tried to activate the reserve. “The reserve parachute went into a spin and she could not gain control over it. She remembered fighting to take control and then everything went black.”

Airfield staff raced to the ploughed field where Victoria Cilliers landed, expecting her to be dead. She was breathing and was airlifted to hospital, where she was treated for a broken pelvis, ribs and vertebrae.

When the parachute was examined one expert called the main parachute the most tangled and knotted he had ever seen after a malfunction. Investigators found that two of four vital components called slinks, which help keep the canopy lines attached to the harness, were missing.

The prosecution claims that Cilliers, who had been trained in packing parachutes, tampered with the main chute and the reserve the day before when he took it into a toilet at the airfield.

The British Parachute Association has said that in the millions of jumps that have taken place in the UK there has never been a double parachute failure and there were no known cases of slinks breaking anywhere in the world.

The jury of nine women and three men was given a bundle of documents containing details of social media messages that the prosecution claims showed Cilliers’s state of mind at the time of the alleged attempted murders.

Bowes said Cilliers had begun a relationship with Stefanie Goller, also a parachutist, after meeting her via Tinder in November 2014. On 25 November he messaged her to say: “I’m at your disposal all day and night.” On 19 December he told her via a message: “Stef, I am not letting you go.”

The court heard that he had lied to Goller in saying he had left his wife four months before. He had also lied that he was not the father of their second child, who had recently been born. Cilliers had said: “I will sacrifice and give up so much for you.”

At the end of February Goller expressed concern that he and she would be seen as the “bad guys” but Cilliers reassured her: “I promise this will be water under the bridge very soon.”

In another message he said: “I’m not going to lose you. You have no idea how much you mean to me. I have a massive urge to be with you. I feel I need you more than ever. I mega adore you.”

Bowes said other messages showed Cilliers was also having sexual relations with his former wife, Carly. The prosecutor said he would not read out the text messages between them as they were explicit but he added: “They discussed what they are going to do and what they had done.”

On Sunday 30 March Cilliers left the family home in Amesbury, Wiltshire, and drove to an army barracks in Surrey, explaining that he wanted to avoid the rush-hour traffic the next morning. The prosecution alleges that before he went he used a tool to loosen a nut on a gas pipe in the kitchen, aiming to cause a leak and an explosion.

Victoria Cilliers smelled gas and messaged her husband: “Are you trying to kill me?” When he asked her what she meant she said she had only been joking and had been reading magazine stories of husbands killing wives.

Bowes said that as Cilliers drove home later he realised that his attempt to kill his wife had failed. Cilliers then texted his wife, inviting her to take part in a parachute jump as a treat, saying: “You want to go jump this weekend?”

The prosecutor said that a sad aspect of the case was how excited Victoria Cilliers had been over the idea of such a treat. She messaged back: “Would love to.”

At the same time Cilliers and Goller were exchanging dozens of love messages. Cilliers asked her: “Have I told you lately I’m massively in love with the most amazing woman in the world? I want my life to start with you now.”

Bowes said those who saw Victoria fall expected her to die. She might have survived because of her slight frame and because the landing zone was a ploughed field.

The trial continues.