He may be 36, but you can still see the angel with the dirty face in actor Paul McGann. His handsomeness - and my God, he is handsome - is undercut with a dangerous edge of unpredictability and the iconoclasm that comes from holding on to one’s origins in a profession that is anything but humble.

Best known for his appearances in the cult film Withnail and I and in the BBC production The Monocled Mutineer, as well as scores of other television and film roles, McGann appears as Bassanio in Channel 4 School’s five-part adaptation of The Merchant of Venice (also featuring Bob Peck and Haydn Gwynne). Shakespeare is pretty much of a new departure for him, but one that he felt would, in his words, “be good for me as an actor”.

It’s also a play that intrigues him. As a young boy growing up in Liverpool 8, his mother would read him, his three brothers - actors every one of them - and his sister bits and pieces of Shakespeare “sort of as a book at bedtime”. One excerpt that stuck in his mind was Shylock’s “If you prick medo I not bleed?” speech.

It was an interesting selection for Mrs McGann to read to her brood. Their neighbourhood in Everton comprised a big, strong Catholic parish of families mainly of Irish descent within a wider community of West Africans, West Indians and Chinese. The McGann boys all went to the primary school “in the shadow of the church” and were altar boys and choir boys on Sundays. “We were these little scally lads with shaven heads and angelic crosses around our necks. ”

The church was so much woven into the fabric of his life that now, when he recalls the changeover from the Latin mass to English, he “can still feel the disappointment and loss”. Perhaps inevitably, after finishing O-levels at his Jesuit grammar, he turned his back on his religion.

But school wasn’t all prayers and cold showers. His head of drama inspired him and was in turn impressed enough with the young scally’s portrayal of Antony in Antony and Cleopatra, as well as appearances in a varied repertoire that took in the young Tom Stoppard and the considerably older Aristophanes, that he encouraged McGann to go for drama school. He made it to RADA and has been making it ever since.

Which brings us back to The Merchant of Venice and his interest in it. He sees it, as do many actors and directors - let alone the rest of us - as a problematic play that provokes myriad questions. “Why do people keep performing it? Is it to tease out some kind of understanding? How has it survived? How much has our society changed since Shakespeare’s time? Were the racist jibes any easier to receive then than now? And I wonder what kids make of the play. How is it presented to them?” Working on the production for Channel 4, which was directed by Alan Horrox of Tetra Films, McGann’s eyes were opened to the complexities of characterisation and the social climate.

“I felt sorry for Shylock. I stood there thinking as my character vilified him, ‘I’m with you, mate’.” Perhaps mum’s book at bedtime readings were coming home to roost.

Horrox’s production is a distilled version specially adapted for 11 to 14-year-olds as part of Channel 4‘s Middle English strand. Pared down to the “bare bones” at 100 minutes, it has, according to McGann, “stuck to the narrative and cut out a lot of waffle. Hopefully, the ambiguities of Shylock survive. And you just hope that the vitality, even the recklessness of Bassanio comes across, rather than just appearing weak-willed”.

For a film and television actor not used to performing Shakespeare, The Merchant of Venice is doubly daunting because of its difficult racism. Added to that, schools television is something that some actors are sniffy about. McGann wasn’t sniffy, but he did start off lacking confidence until he got the hang of it. And then he loved it. “It was a hoot. In parts it was impenetrable and in other parts, it was camp and funny. I had to wear the full thing - codpiece and wig - and it was all the better for it.

“There’s enough polo-necked versions of tight-arsed Shakespeare around. But your responsibility is to make it understandable for kids, which is tricky. We were having to balance the natural theatricality of the thing with working on film in a register that was truthful.”

Can we expect to see the utterly delectable Paul McGann don yet more wigs and tights in the name of educating the nation’s young? Has he cracked the Bard? Who knows? But of the fact that he has been moved by performing Shakespeare, he is certain.

“The key to Shakespeare is when it gets you where you live. I remember the priest who was directing us in our school Antony and Cleopatra saying to me, ‘do you understand this, that “love conquers all”?’ And I thought about it for a while and it became clear to me. That’s the sort of thing that gets you where you live.”