Interviewers should be able to pack a punch, but Humphrys has a severe, sardonic streak. It may serve a purpose in the cut-and- thrust of the Today programme, but it's counter-productive over longer stretches.
Humphrys's first aim seemed to be to get the former minister to admit that he was ambitious. Mellor wouldn't do so, arguing his case with torrents of articulacy. You could believe him or not - but what you couldn't dispute was the thoroughness of his self-analysis. It wasn't good enough for Humphrys - Mellor hadn't said what he wanted him to, and he pursued the point long after it was clear that it would not be conceded.
Interviewees as skilled as David Mellor need subtler handling if they are to be drawn out. This was more naturally the territory of Anthony Clare or Sue Lawley than Humphrys, whose provocative, journalistic approach - the need to put the subject on the spot - made for unsatisfactory listening. By the end we knew little more about Mellor than we did already.
For the self-revelation that radio does so well, there has been a remarkable voice to listen to this past fortnight - that of Brian Keenan, in A Book at Bedtime (R4). His account of life - if you could call it that - as a Beirut hostage caressed the ear and stole the heart.
When it came out last autumn, An Evil Cradling (or An Anvil Cradling as one Radio 4 announcer called it) astonished the critics with its fluency, deftness, and power to express the inexpressible. Hearing this most acutely personal of stories told by the author himself has given it another dimension altogether.
Keenan's diction is soft, his delivery tender and lilting: a lovely contrast with the story he had to tell. But there was no trace of a 'performance'. In their prison cell, Keenan may, as he put it, have 'laid on my Irishness thick and creamy' for John McCarthy's benefit, but the listener wasn't being manipulated - just gripped by this glimpse of the universe that can be contained within a man's mind.
Keenan added a couple of accents - a guttural harshness for his guards, exaggerated English public school for McCarthy - but these were merely touching in their amateurishness. Of many memorable scenes, the passage describing his first meeting with McCarthy - the sports-jacketed journalist, sitting on the cell floor, uncertainly removing his blindfold as a bemused Keenan peers down at him - stood out as a piece of sustained tension.
Keenan's more Proustian reflections worked just as well in a medium made for turning thoughts into pictures. He peels an egg, pondering the word 'albumen'. He is given an orange, the first fruit he has seen for months, and wants not to eat it, just to touch it. And then there were the moments of pure Samuel Beckett, as Keenan and McCarthy - in an extraordinary echo of Vladimir and Estragon in Waiting for Godot - stood in the darkness absurdly trying to out-hurl insults at each other.
This was a memorable 10 nights of radio. One was left marvelling at the man, and wondering what else could be found for him to write and talk about. Both voice and sensibility are too good to vanish into thin airwaves.
The person I felt sorriest for last week (not including Brian Keenan) was Gill Pyrah, presenter of Tuesday's Kaleidoscope (R4) in which it fell to her to interview Eddi Reader, former lead singer with Fairground Attraction, and a couple of fellow musicians. This was a throwback to the much-parodied encounter you used to get on The Old Grey Whistle Test on BBC2. Interviewer asks sensible question, interviewee giggles. Interviewer asks another sensible question, interviewee says nothing. Interviewer asks third sensible question, and interviewee and friends all start blathering incoherently.
It comes as a surprise when a pop singer turns out to be as articulate as the stereotypical footballer. And all the more so when they turn up on Kaleidoscope. The programme may be much more relaxed and middle-brow than it was, and there's nothing wrong with that. But this was taking things too far. Ms Reader should stick to singing. Perhaps the problem was that someone had already told her that.
Radio men who upped and left the homestead and discovered the big city of television are returning to their roots, or at least are visiting again. First Terry Wogan, now Desmond Lynam.
To be both smooth and nice is a rare combination, but this is Lynam's great gift, and it's there to enjoy again in a new series of They Think It's All Over (R5), the sports quiz whose spirit is closer to Have I Got News For You than A Question of Sport. The sporting guests - in this case Steve Davis and Roger Black - seem to thrive on the format, too. It must be such a bore to be taken seriously all the time, but with Lynam there's no chance of that.