It’s a singer’s worst nightmare. Jonathan Veira, due to sing the title role in Verdi’s opera Falstaff in Glyndebourne on Tour’s new production, is sitting in his dressing room at the New Victoria Theatre, Woking, surrounded by pills, tissues, and bottles of soothing throat medicine.

“I woke up at three this morning, went downstairs – much to the annoyance of my wife – and started checking whether I had any voice at all,” he told me. There was only one consolation: he could at least go home and sleep in his own bed after the performance.

“Home is only ten minutes away. Apart from doing concerts in Guildford Cathedral, this is the only time, ever, that I get to perform this close to home. The trouble is that local friends are coming to see me tonight. And now it’s the one occasion that I’m ill.”

Arriving at the stage door, I was firmly told that Jonathan would only be allowed to talk to me for a maximum of ten minutes – entirely understandable in the circumstances. But such is his immense and infectious enthusiasm for Falstaff – he’s sung the role more than 80 times in six different productions – there was no stopping him.

“Falstaff is almost quintessentially English. People kind of admire him from afar. They’ve never been that way themselves – generally people are not bawdy, they’re not drunk like Falstaff, although drunken louts in the middle of cities might behave like that. For me, as an actor, he’s a gift of a role. It’s just the most perfect part, because it has everything, including the chance to play comedy, which is how I spend my life.”

Reviewers commenting on the Glyndebourne Festival performances this summer described Falstaff as not only drunk and debauched, but also as “displaying overweening self-confidence”. That last characteristic could put you in mind of certain recently disgraced bank bosses, I suggested.

“Absolutely: I think the parallels are a bit too disturbing! He is an overweening, self-confident man, who believes that he is still – given his rather fulsome body – a wow to women. He needs money, he needs alcohol, he’s a man of excesses in everything that he does. At the end of the opera he says: ‘I’m the salt in the meat.’ But the key point about Falstaff is his depth of character. So when people talk about him being bawdy and rowdy, he’s actually multi-dimensional – to see him from only one dimension is to not see him at all.”

Glyndebourne’s production is set in the 1940s, and Falstaff is seen holding court in his local pub – an imposing mock-Tudor emporium, complete with stag’s head over the fireplace. His paunch barely covered by a double-breasted suit, he is spluttering over the cost of 30 bottles of sherry, which have mounted up on his slate. He seems the epitome of the pub bore – the regular everyone tries to avoid.

“He will certainly be a regular, everybody knows him,” Jonathan agreed. “That’s part of the attraction of the man: he’s the local guy about whom everybody says: ‘Oh no, we’re not going to be stuck with him all evening, are we? He told us that story last week, and last year.’ And whatever you’ve done, he’s done it better. But in fact he probably has done it better – the experiences he’s had are so vast. I love that.”

Falstaff is by tradition fat, and Jonathan Veira is not. It was time to cross the dressing room and inspect the massive stomach, hanging on the clothes rack.

“It’s very heavy, and I sweat an awful lot in it,” Jonathan exclaimed with feeling. “Falstaff has to be fat: there’s this great big moment, which I don’t think I’ll be able to manage tonight, when he sings that his stomach is his throne, and it’s going to grow and grow. This is his empire. If a production tried to make him tiny, I’d have to argue big time. People wouldn’t love him if he wasn’t fat.”

It’s time for Jonathan Veira to start dressing for the performance, and take a glance at the well-thumbed score sitting in front of him.

“I’ve got a terrible memory, I’ve got so many operas stored in there. When I’m dead and gone, they’ll cut me open and contribute my brain to modern languages – I’ve got a lot of Czech, a lot of Italian – and out will come millions of words.”

Falstaff is at Milton Keynes Theatre on November 25 and 28. GOT are also presenting Mozart’s Così fan Tutte (November 24 and 27), and Janacek’s Jenufa (26). Tickets 0844 871 7652 or www.ambassadortickets.com/ miltonkeynes