Friday lunchtimes are often a little longer than during the rest of the working week, but today “popping out to grab a sandwich” might just take all afternoon.

Andy Murray will step out on to the Centre Court for his semi-final against Andy Roddick at some point around mid-afternoon today — almost as soon as the clash between Roger Federer and Tommy Haas, which starts at 1pm, is completed.

For long-term tennis fans and the legions who have converted during this Wimbledon fortnight, that’s when the weekend starts. As Murray Mania reaches fever pitch, those suffering from this contagious affliction will congregate around big screens in towns from Edinburgh to Portsmouth to cheer on the 22-year-old Scot.

While Murray will stay dry, thanks to Centre Court’s new roof, people watching outdoors might have to put up with a little rain on their strawberries if the forecast for showers proves accurate.

This evening, sometime after 5pm, the fans will also be able to shout for Andy’s brother Jamie, who is in the semi-finals of the mixed doubles with his partner Liezel Huber. If the pair are victorious, Jamie will be in with a chance of his second Wimbledon title after winning the mixed doubles in 2007 with Jelena Janovic.

Pubs, bars and clubhouses will all be too happy to offer shelter, plus discounted Pimm’s and “Perfect Serve” cocktails — or the traditional tennis drink of Barley water for more sober viewers. For those tuning in from the comfort of their sofas, a white wine called Mighty Murray is on special offer at certain supermarkets (we’ll gloss over the fact that it’s Australian).

Yesterday, the CBI pleaded with people to turn up at the office: “Many employers will be flexible about letting staff watch the match, but it’s not fair on colleagues or employers if staff phone in sick or knock off early without permission,” said Katja Hall, director of human resources policy.

Meanwhile, in Murray’s home town of Dunblane, there are already banners pinned to the fences of the sports club’s tennis courts: “Good Luck Andy”, reads one. “Well Done Andy”, says another, demonstrating that the locals will be proud whatever happens.

John Hill, the butcher’s shop on the town’s picturesque High Street, has organised an early breakfast barbecue to feed early-rising residents this morning, not to mention the television crews who have descended in the hope of catching the triumph of a local hero.

Local landlords are also primed for a brisk day’s business and every shop has a poster in its window. Saltire and Union flags flutter from poles or are draped over walls.

More than 400 miles south at the All England Club yesterday, the buzz was as much about Murray as the Williams sisters, who powered their way through to the women’s final.

Many fans who had enjoyed watching the women’s semi-finals in sweltering sun were nevertheless envious of those who will be in their seats today for the men’s matches.

Anita Satsangi, a 46-year-old management consultant, said she would be forced to quietly monitor proceedings from the office: “I will have to try to watch the match at work if I can and sneak a peak at the results on the website. Maybe I can have the television on as long as I don’t turn the sound up. I would love to have come tomorrow.”

Others said they would return to the grounds, despite having no ticket for the Centre Court, to soak up the atmosphere and watch the big screen from Henman Hill — Murray Mount (delete according to allegiance).

Panos Conti, 37, was less enthusiastic: “If I had my way, we wouldn’t have any Brits at Wimbledon to save us all the hysteria.” He did, however, admit that he would be watching at home in Wandsworth. Failing the national disaster that would be a Roddick victory today, Murray Mania can only intensify before Sunday’s final.

Die-hard fans are already begging, stealing and borrowing for a chance to watch the potentially historic fixture, and the blogosphere is rife with talk of a British Wimbledon champion at last. Reports of tickets for the final changing hands for five-figure sums do not impress everyone, however.

Ernie, a Times Online reader from Bradford, said: “As we say in Yorkshire, they’ve more brass than sense!”