Johnny Depp thanked Amber Heard for getting him “clean” on a detox trip to his private island in the Bahamas and told her mother that, without the help of his then-fiancee, he “wouldn’t be alive”.

The Hollywood A-lister told London’s High Court that withdrawing from drugs was “agonising”, and said he was at the “lowest point I believe I have ever been in my life” during the August 2014 trip.

At that stage the couple were engaged to be married.

During a text exchange between the actor and his ex-mother-in-law, Paige Heard, sent at that time, Mr Depp said his fiancee had “risen far above the nightmarish task of taking care of this poor old junkie”.

Reading the texts, Sasha Wass QC, for News Group Newspapers (NGN), explained that Paige Heard’s use of the phrase “my son out-law” was a joke between the pair.

The text message to Mr Depp read: “You’ve gotten through the hardest part, it may be hard to see, but you will be so glad to have this gorilla off of your back.

“I’ve seen the hell this addiction brings and I wouldn’t wish this on anyone.

“You are a big wonderful man to break the cycle. Please let me know if I can help in any way. All my love.”

In a lengthy response Mr Depp described the message as “unbelievably kind and pure”, and said he was “beyond thankful” to have Paige Heard in his life.

He added: “What you do need to know is that your daughter has risen far above the nightmarish task of taking care of this poor old junkie.

“Never a second has gone by that she didn’t look out for me or have her eyes on me to make sure that I was OK.

“My words are truly feeble in attempting to explain her heroism in a text – suffice to say that I have never met or loved a woman or a thing more.

“She has the strength of a thousand men, and that is due to no one or nothing but you sweetheart. Thank you, I love you.”

He said he “couldn’t have made it without” Amber, and added: “If you’d have seen her in action – amazing.”

He went on: “It was an exercise of monumental patience and instinct. I wouldn’t be alive, sweetheart.

“There were more than a few times when I thought it would be more simple to take that route.

“It was Amber and Amber only that got me through this, and it was not easy.”

In court on Thursday, Mr Depp said the messages to his mother-in-law were him saying good things about a daughter to her mother.

Ms Wass also read a text sent by Mr Depp to Amber Heard which read: “Thank you so much for getting me f****** clean baby.”

Mr Depp told the court he recalled “a great deal of pain and uncontrollable spasms” during the detox.

In his witness statement, the actor claimed that Amber “often intervened and withheld medicine from me” while the couple were on the island, which he described as “one of the cruellest things that she has ever done”.

But Ms Wass said that assertion about withholding his medication was “not substantiated by any evidence”.

Mr Depp replied that he could not say whether it was substantiated, adding that he might have been due to get medication by 4pm but got the “heebie-jeebies” by about 3.15pm and would start shaking and having stomach cramps.

He said he told his fiancee he needed his medication, but that she said “No, four o’clock”.

He said: “My body clock was needing medication to stop the onslaught … I was not in good shape.

“For someone this low – it is the lowest point I believe I have ever been in my life – on the floor, sobbing like a child and had still not received the medicine.”

Mr Depp denied pushing or attacking Ms Heard, saying he was in “in no physical condition to push anyone”.

A text from Ms Heard to Debbie Lloyd, a nurse who was staying on the other side of the island, was read to the court, which said: “Issue has arisen again. He took the meds about 30 minutes ago.”

It added: “He was so mad he pushed me and I asked him to get out. Don’t know what to do. Sorry to keep at you guys.”

Mr Depp repeated what he had said in court on Wednesday, that Ms Heard’s allegations were part of an “insurance policy”.