In the witness box, Mr Mills said life with Mrs Mills had been “really good” and he was “devastated” to learn of her affair after the attack.
He said he knew Mr Berry through charity work and had questioned Mrs Mills about the time she spent with him, but she reassured him: “There’s nothing going on, it’s just work, and I love you.”
Mr Mills told the court they had eaten dinner together in their caravan that night, listening to music and having a few drinks, before a knock came at the door at about 23:30 BST.
“Michelle had been on her phone,” he said. “I assumed she was playing a game – apparently not.
“As I opened the door he literally hit me right in the face with a pistol, ‘get back’, ‘get down’, he was saying.
“I punched him in his face. I pulled his pistol off of him. He was dressed in overalls, with balaclavas. He was a lot bigger than me,” Mr Mills added.
He said there was someone else there too, who he fought off, and then his wife called the police.
Mr Mills also confirmed he drove the Mini Cooper S when questioned by the prosecution.
Footage of Mrs Mills’ arrest showed her saying: “I’m going to end up in prison because of this.”
Defence barrister Caroline Rees KC suggested the marriage was not as happy as Mr Mills claimed, but he replied: “I never suggested I wanted a divorce,” rejecting suggestions he could be controlling.
The court heard he had been arrested, a day after this attack, on suspicion of domestic violence.
“My heart sank,” he said, “I knew at that point that she was involved in this debacle.
“All I kept saying was, this is all wrong, my wife must have been involved in this, I’ve never touched her,” Mr Mills added.
The trial continues.