In recent months, the TV personality has been spending time out of the public eye and in the 12-minute clip, he explained he decided to do so in order to recover privately, after having his prostate removed.
Speaking of how his diagnosis came after a routine check-up, Stephen said: “I went to see my doctor just before Christmas for a flu jab. I’d heard it was going to be a bit bad this year so I thought maybe a flu jab would be a good idea.
“So I went to see my doctor, Tony, he was at my school a year or two above me and he’s been my doctor for a couple of years. He said let’s have a checkup, an MOT, I have one of these every year.
“I had my blood taken, urine and blood pressure, pulse [checked] and tapping here and there, general procedure, nothing to worry about.
“The next day he called me up and said I’m a little worried about your PSA levels. It stands for prostate specific antigen and these are the things the prostrate gives out if its under attack from something like a tumour.”
Stephen then went for an MRI scan, where the diagnosis was confirmed.
“The prostate is an absolutely prone bugger for cancer,” he continued. “There you go, I’ve said the c-word now.”
The MRI scan was followed by a biopsy and a PET scan, and with a team of healthcare professionals, Stephen decided on the best course of action.
“We had a couple of options,” he explained. “One was radiotherapy but that’s a long and very difficult process.
“That’s fine for some people but there are a number of issues with it for me, I won’t go into the full details of it.
“And the other was to get rid of the prostate - to get it out - and that’s the operation we decided on. He [the doctor] also wanted to take out some of the lymph nodes just in case.”
Since having the operation in the first week of January, Stephen has been spending time resting up, with the support of his family and a few close friends.
“You think you’re going to recover really well but it takes longer than it might and it’s all pretty undignified and unfortunate,” he admitted. “My family and my divine and darling husband were just marvelous and those few friends who have known have been very kind and discreet about it.
“Cancer is a word that just rings on your head. you don’t think it’s going to happen to you, cancer is something that happens to other people. What a horrible word it is.”
“So far as we know it’s all been got. Are there greater chances of me getting other cancers now? Apparently not. But I won’t know for sure until my PSA levels are checked.
“But for the moment, I’m fit and well and happy and I just wanted you to know, because rumors had started to swell.”
He then revealed his reason for sharing the news, adding: “A newspaper had called up and I thought well before the gossip gets silly and ill-informed, I will come clean so there you are.”
Earlier this month, Stephen was absent from the Baftas for the first time in eight years, with Joanna Lumley taking over hosting duties.
Announcing his decision in January, he said: “Over the last two decades I have especially loved watching the emergence of new young film talent behind and in front of the camera. But after so long a time I felt it only right to stand down and let others take the Baftas on to new heights and greater glories.
“What fun it will be to watch Bafta 2018 without my heart hammering, mouth drying and knees trembling.”