He could see his wife was “having a good day” when he arrived at the Ty Pentwyn Nursing Home.
Mrs Oliver, 85, clearly recognised her husband as she was wheeled in by her carers to her room at the care home.
The couple smiled and the room fell silent when her husband asked her if she had missed him. “Yes,” she replied.
It was the first time the Oliver family had come into contact with anyone from the Jewish community and the couple’s son, David, paid tribute to the US volunteers who had made the 360-mile round trip.
“It is amazing how far they have come to drive dad around the corner,” he said. “It means a lot to us.”
He visits his mother every day and had been trying to arrange for a private ambulance to take his father to her care home, only to be frustrated by “red tape”.
He was both impressed and relieved when the Ambulance Wish Foundation UK said there were Jewish volunteers from London willing to make it happen.
Driving the ambulance was paramedic and Stanmore Synagogue member Saul Gaunt.
The 26-year-old London ambulance driver has overseen the training of 36 volunteers from the US, who will complete future trips in the ambulance.
For the journey to Wales, he had arrived at Friern Barnet ambulance station with volunteers Dave Kurash and Peter Phillips at 5.45am.
“This is the first we have done,” he said. “But we hope to do many more. We want to help people fulfil their final wish. It doesn’t matter if they are not Jewish.”
He added that Rebbetzen Freda Kaplan, former Rebbetzen of Hampstead Garden Suburb United Synagogue, had raised the money to buy the ambulance, which had been donated to the foundation.
“They needed volunteers, which is why they approached the United Synagogue.
“I went down for a meeting thinking I was just going to be advising them. The next thing I knew, I was training everyone.”
The volunteers have received an accredited first-aid qualification and been trained in end-of-life care.
“It is quite difficult to get people who can take a full day off work for something like this,” Mr Gaunt pointed out.
“But I put the call out to our WhatsApp group when Derek’s wish came in Dave and Peter came back straightaway.”
Mr Phillips, a property manager, said he had not slept the night before.
“I was waking up on the hour just thinking about what we were going to do. I didn’t want to miss my alarm.
“It was really clear from the moment we arrived how much it meant to Derek. He loved his wife and missed her terribly. To be able to facilitate that wish is priceless.”
Mr Kurash, a driver for Addison Lee, “hadn’t known what to expect from the experience”.
But after dropping off Mr Oliver, the 54-year-old said he felt he had performed the biggest mitzvah possible.
The volunteers had driven “a really long way” to make a return trip taking at most around 20 minutes. But nothing could compare with “what we managed to achieve”.
He had helped lift a fragile Mr Oliver out of his bed onto the wheelchair that would take him to the ambulance stretcher.
The couple were able to spend two precious hours together at the care home before he was taken back.
“They both thought they weren’t going to see each other again,” David Oliver said. "They have been together for, I think, 59 years and married for 57.
“He was mentioning to the carers, ‘I miss my wife’. And every time I visited my mum she was asking about my father.
“I honestly thought, up until Monday, this is one promise that I’m not going to be able to keep.
“I have thought about it every day. I have wanted this for months and months.”
Derek Oliver said the enforced separation from his wife had been painful.
“When you are married that long, you miss them when they go out of the house. At the end of January, as I was leaving her, I said ‘I’ll see you tomorrow’. I haven’t seen her since.”
Despite his obviously frailty, he was in good spirits throughout the ambulance journey, the diabetes sufferer joking about his fondness for cake.
He told the volunteers that the secret to a long and happy marriage was simple: “You stick together, don’t you?”
