Description of a flight through a nuclear mushroom cloud

The BBC's Keith Moore tells the tragic story of Joe Pasquini, an RAF navigator who was ordered to fly a jet through the mushroom cloud rising from the 1958 Grapple Y nuclear test, the largest nuclear explosion ever created by the British (he also flew through the Grapple Z test). He has since survived seven bouts with cancer; his children have also had various cancers. They blame his exposure to nuclear radiation, but have been denied any benefits by the British government, which, unlike the US military, does not acknowledge that veterans of nuclear tests are at any elevated risk of cancer. Here's Pasquini's description of his flight through the heart of a mushroom cloud:

"It detonated at 8,000 feet. We had our eyes closed, but even with our eyes closed we could see the light through our eye lids. It took 49 seconds for the light to stop.
"As soon as that happened, we immediately turned back. Fortunately being in the navigating position, I had a little window and I watched the whole thing develop and spread and then start climbing.
"I think I saw the face of God for the first time. It was just incredible, it blew our minds away. These were things that had never been seen before, certainly not by English people."
When the mushroom cloud had passed over them, Pasquini looked up at the window above him and had another surprise - radioactive rain.
"It's the only time I've experienced rain at 46,000 feet," he says.

Nuclear test veteran who flew through a mushroom cloud