Enter Mr Tennant Centre Stage

WE HAVE just had a mordantly funny Morecambe and Wise moment. Romeo is skulking in the background, desperately trying to catch his friend Benvolio's eye as their mate Mercutio makes one filthy pun after another. Each attempt by the two young men to make eye contact ends with everybody in the room corpsing with laughter.

"It's pure Eric and Ernie, isn't it?" murmurs Michael Boyd, the Royal Shakespeare Company director rehearsing Shakespeare's romantic tragedy prior to its Stratford-upon-Avon opening.

It was Bathgate-born actor David Tennant's idea that they should introduce this bit of business into Act II, scene 1, when the hung-over Montague lads go in search of Romeo. "You were doing an Eric," Boyd grins at Tennant, the lanky 29-year-old playing Romeo. "No, I wasn't," denies Tennant. "I was pushing energy up from the back of the stage."

"Yeah, well, much as we all love Eric and Ernie, and Shirley Bassey tripping up over the scenery, let us forget that idea and get back to the main business of this scene. Which is everybody talking about shagging," Boyd declares unequivocally.

Tennant, Adrian Schiller (Mercutio) and Anthony Howell (Benvolio) sit down around the director's table and pore over their Arden texts of the play. They work their way through academic footnote after footnote. It is like a masterclass on Elizabethan English and dirty Bardic jokes. "You have to know what you are talking about, otherwise you end up running scared of the words and not trusting Shakespeare," says Tennant later.

So, there is much talk about medlars - a fruit only eaten when rotten - and Elizabethan forms of contraception, while Tennant, youngest son of former Moderator of the Church of Scotland, Sandy McDonald, poses questions like: "When I enter for this scene, do I come out of the fallopian tube?", referring to a part of the set.

One of theatre's big discoveries, Tennant arrived at Stratford in January to start rehearsing his lead role in The Rivals. At the same time he rehearsed another starring part, that of the twin Antipholus in The Comedy of Errors. Both have opened to rave reviews and Tennant has won much praise for his performances. As Boyd, former artistic director of Glasgow's Tron theatre, describes, "He has a tremendous ability to communicate with an audience - he's like an open book. He has such an open face and an open spirit."

In The Rivals, one critic wrote that he "is blessed with the most eloquent left eyebrow since Roger Moore's". Another said of him in The Comedy of Errors: "Tennant's ingenuity and understated comedy are the production's making. His face speaks volumes and is as changeable as a weather-vane." And a third: "The best performance comes from David Tennant... rapidly establishing himself as one of the most endearing comic actors in the business." Not that you dare quote any of these to "the skinny Scot frae Paisley".

There is no time for reading reviews, he says, as we race down the stairs behind the scenes at the theatre and rush across to the Union Club, the RSC's version of the Groucho Club-on-Avon for company members, to dive into steak and kidney pie and coffee cake. He will read all his notices at the end of the season, when he will have played 97 performances as Jack Absolute, slid down the banisters as Antipholus 72 times and fallen in doomed love with Juliet 45 times.

There have been two matinees every week, as well as six evening shows since The Rivals started previewing in March. "I don't want to know the total number," he says, as I prepare to quote the statistics. "I haven't dared count them. It's too terrifying, although once Romeo and Juliet opens I'll just be doing eight shows a week and getting days off, because I won't be rehearsing."

Tennant reckons he gets his first Monday off in August. "But to make up for it, we then do three matinees. I get a very short break in September, I think. It's quite full on, but it's that or you don't do the parts.

"He is perfect casting for Romeo, because of the intensity he brings to his work," Michael Boyd says. While Tennant's great friend and former landlady, the comic performer and author of Does My Bum Look Big in This?, Arabella Weir, says: "He's astonishingly focused for his age and amazingly straightforward and honest. He's trustworthy and he's honourable."

Tennant lodged with her for five years when he "very trepidatiously" moved to London. Weir, whom he met on Takin' Over the Asylum, led him astray, he jokes. "She would shock me with the things she would say, but she finds it harder to shock me now. She probably corrupted me, but I probably needed corrupting a little bit. It sounds like we were lovers or something. We weren't. It was more she led me into the murky world of London. I think I was quite green when I left Scotland - I was blessed with a very good upbringing, because my parents are very moral, Christian people, but without all the brimstone and thunder nonsense."

There is still something uncynical and unspoilt about him, though. He confesses that being with the RSC can be scary. "Not only because you are in the home of 'world class classical theatre' (as all the brochures tell you), but these big Shakespearean roles come with a lot of historical baggage attached. People tell you how romantic Ian McKellen was as Romeo, or how masculine Sean Bean was, or how marvellous Laurence Olivier was. You feel the weight of all those ghosts, those performances that have taken on a mystical resonance. And because it's Shakespeare, you feel it's hard to make it believable, because it is so beautiful.

"With this play, everyone has so many ideas about it, that you almost want to play against the beauty. We did the balcony scene the other day and I was doing: 'But, soft! What light through yonder window breaks? It is the east, and Juliet is the sun!' And I was going: 'How can I say that?' It is beyond parody, but all you can do is be personal with it and make it your own, if that doesn't sound too pretentious. I know that's how Alex [who plays Juliet] feels about famous lines like, 'Parting is such sweet sorrow'."

Rehearsals carry on into the evening, although Tennant has to dash off to a warm-up, then strut his stuff in The Rivals. The last "Bravo!" is still echoing in his ears as he flies out of the stage door, clutching his shopping. "The milk and the orange juice will be curdled. They have been in my dressing-room all day," he says gloomily. There is not even time for a post-show pint in the actors' local, the Dirty Duck. He has, he notes, only been there twice since January. "I'll make up for it once Romeo's up and running," he promises.

After the show, which finishes at 10.30pm, he drives the mile-and-a-bit to his flat, watches TV for half an hour to unwind, and then goes to bed with the Arden edition of "the greatest love story ever told". Then, the next morning, he's up at 8am, eats a bowl of Honey Nut Shredded Wheat - "my only concession to healthy living" - and drives back to the theatre, where he showers, goes shopping at Marks & Spencer for lunch, then starts rehearsals again at 10am. "I'm marrying Juliet this morning," he says. "Knowing Michael, it'll be something unusual and different. Swinging from the chandeliers? Probably."

The intensity of the rollercoaster he is on is overwhelming. Stratford is a gruelling, sometimes stifling, hothouse. Rehearsal followed by show, followed by rehearsal, in one long punishing schedule. After one-and-a-half hours in the rehearsal room, there is just time for a snack before voice warm-ups for the matinee of The Rivals. There, Tennant's rapier-thin young blade gets involved in sword fights and various cunning derring-do disguises, then he is off again for lunch. And back on again, for The Comedy of Errors. A short show, but a physical one, as Tennant slides down those banisters, executes pratfalls and turns in a brilliantly funny double act with Ian Hughes, who plays his manservant, Dromio. He also does the neatly witty trick of lighting two post-coital cigarettes after seducing his long lost twin's wife and then buries his head in Nina Conti's cleavage.

In the interval, I watch as a group of giggling schoolgirls reading their programmes, discover Tennant is to play Romeo, and spend 15 minutes chanting: "Wherefore art thou Romeo?" Since Leonardo DiCaprio's film rendition, Romeo and Juliet has to be the most popular of plays amongst teenagers. A reason to come back for more, even if this Romeo isn't Leo.

Later Tennant is in his dressing-room, stripped to the waist, slapping Simple moisturiser onto his face, swigging pints of mineral water, and packing up his make-up box, an old-fashioned leather bowling case. As we leave, we trip up over a bloody but unbowed Hotspur, about to go on stage and die in Henry IV, Part 1. Falstaff is plumped in the corner and wishes us a courteous good night, while various make-up girls daub elderly knights. "It's like this every night at this time," says Tennant. "You can't move for men in armour and there's blood everywhere."

There is still no time for one quick drink in the Union Club. "I've got to get those lines fixed," he says, as he climbs into his car. He pushes a taped version of Romeo and Juliet - in which he plays Mercutio and Joseph Fiennes is Romeo - into the recorder. "It'll help me with learning my lines and, hopefully, Joe might have come up with something new that I can nick for my performance." And he drives off into the Warwickshire night.

Romeo and Juliet runs until October 7, in the Royal Shakespeare Theatre at Stratford-upon-Avon. The Comedy of Errors runs until October 6 and The Rivals is in the Swan Theatre until October 7.