The father of brain tumour boy Ashya King has said trying to save his son was "worth going to prison" because the treatment he received in England was going to "kill him or turn him into a vegetable".
Brett King and his wife Naghmeh King described their anguish at being separated from him after they were arrested and held in a Spanish prison for almost four days.
As they prepared to see their son for the first time since they were detained on Saturday, Mr King said his heart was "aching" while his wife Naghmeh said she had been "crying and crying" in a prison cell.
Mr King said: "My son's worth everything, worth me going to prison, worth everything because they were going to kill him in England or turn him into a vegetable."
He told the BBC: "My heart is aching for my son. I want to see my son's face."
Asked what the ordeal had been like, Mrs King said: "All I was doing all the time was crying and crying. What could I do in a prison cell?"
The couple were freed last night after British authorities abandoned their attempts to extradite them amid a public backlash.
Asked how angry they were, Mr King said: "I wouldn't say angry, I'm just missing my son so much. Anger can't come in at the moment because I've just got these feelings I've got to see my son's face."
The boy's mother said: "I just want to wet his mouth because he can't drink through his mouth, I want to brush his teeth, I want to turn him side to side every 15 minutes because he can't move. I just want to do all those things I was doing from Southampton, I want to do it for him here."
Asked about being separated from her son, she said: "I was just praying so I could be reunited with him again. I couldn't do much, really - all I could do was just cry and pray."
Speaking later at a press conference, Mr King told of the anguish of hearing his wife crying from his cell in Soto del Real prison near Madrid.
His voice breaking with emotion, he described the couple's desperation to see Ashya because he "hasn't got too many months to live".
Mr King said: "When we were in prison there wasn't a minute that went by without our hearts hurting to see Ashya. My wife spent most of the time crying in the cell.
"I was going to ask to move cells because I was worried and I couldn't listen to my wife crying. When you are locked up you can't do anything."
Mr King described the uncertainty they faced about their son's condition after they were detained.
"What is going to happen to Ashya without us? We didn't know what was happening because they arrested us and directly they took our son away.
"We said 'You don't even really know what's wrong with him. He needs therapy on his legs, on his arms. You need to turn him from side to side.'
"But they're not interested. They just want to take him away from us."
He said he does not "feel good" but added: "Hopefully now we can see our son, we can be together and show love to him because without that there's no purpose to life.
"We just want to help my son get through this bad time because he hasn't got too many months to live and we are locked away in a cell. No-one can do anything.
"We are trying to speed things up to help him as much as possible."
He thanked David Cameron and "anyone who has helped release us".
The couple are now expected to travel from Seville, where the press conference was held, to Malaga, where their son is being treated.
They are hoping to take him to a hospital in Prague to receive proton beam treatment.
The Proton Medical Centre said it had received the boy's medical notes and was ready to begin treatment.
Dr Jiri Kubes, head of proton therapy at Proton Therapy Center Czech, said: "We have agreed that proton therapy is a suitable method of treatment for Ashya.
"So, Ashya shall go for proton therapy to the Czech Republic. However, prior to this he will need to return to England first."
Brett And Naghmeh King Leave Prison