A tweeted announcement: Britain gets ready for a 21st-century royal wedding

The souvenir mugs and T-shirts are already on eBay. The bookies favour a date in July, and one punter has put £1,000 on a Kenyan honeymoon. Britain has another royal wedding to look forward to and, amid a wave of officially sanctioned euphoria, the nation has already developed a severe case of "Wills and Kate" mania.

The widely anticipated announcement of the betrothal of Prince William and Kate Middleton yesterday fired the starting pistol on a race to provide everything necessary for suitably flag-waving nuptials, from millions of commemorative tea towels to an appropriately British dress for the bride.

While republicans called for the House of Windsor to foot the bill in a time of austerity, and former palace insiders predicted a new generation of lasting royal marriages, the first signs of an estimated £500m wedding windfall came within hours of the official bulletin being released – naturally – on to Twitter and Facebook.

Memorabilia was instantly available on eBay (£7.95 for a "Kate and William 2011" mug), while one souvenir producer said it had started manufacturing pre-prepared designs straight after the announcement, in anticipation of a 40 per cent increase in trade.

John Wallis, sales director of Aynsley China, which expects its first "royal" bone china to hit the shops by the new year, said: "We'll be making items to commemorate both the engagement and the wedding. Royal weddings are always very popular with collectors all over the world."

The bookmaker William Hill is taking dozens of bets from gamblers willing to take odds ranging from 1-12 on Prince Harry being the best man to 10,000-1 on the potential future Queen Catherine arriving for her big day sporting Elizabeth Duke jewellery and heading with the second in line to the throne to a honeymoon in Magaluf. A spokesman said: "It is a brisk market."

To what extent this reflected what David Cameron characterised as "a great day for our country" remained unclear, but there was at least no doubting the sense of excitement that swept the highest offices of the land shortly after 11am yesterday.

Mr Cameron, who revealed that as a 14-year-old he had slept out on the Mall the day before the wedding in 1981 of Prince Charles and Lady Diana Spencer, said the latest announcement had led to a "great banging on the table" during Cabinet, adding: "It is incredibly exciting news, and I'm sure that the whole country will want to pass their very best wishes to the happy couple, and wish them an incredibly long and happy life together."

The Queen, and the parents of Ms Middleton, likewise offered their warmest wishes to the pair, who are both 28 and became engaged last month during a holiday in Kenya.

They will live in North Wales after the wedding, allowing William to continue his career as an RAF search-and-rescue helicopter pilot. Throughout proceedings yesterday, there was also a sense of history. In the couple's first appearance before the cameras, William revealed he had given his fiancée the sapphire and diamond engagement ring his mother received as a painfully camera-shy 21-year-old.

Ms Middleton, meanwhile, displayed some of the confidence for which she has been lauded. Asked about her future role as a royal, Ms Middleton said: "It is a daunting prospect. Hopefully I will take it in my stride."

Ms Middleton, whose patient wait for a proposal and decision to work for her family firm rather than pursue an independent career had earned her the sobriquet "Waity Katy", will be the first non-aristocrat to marry an heir-presumptive since Anne Hyde secretly wed the future James II in 1659.

But while the daughter of Michael and Carole Middleton, a former British Airways dispatcher and stewardess respectively, cannot claim aristocratic lineage, she is safely from the higher echelons of British society.

The success of her parents' Berkshire-based business selling toys and party supplies has made them millionaires, and their eldest daughter attended the £15,000-a-year Marlborough College before going to St Andrews University, where she met William in 2001 while they were both studying history of art.

Despite weeks of rumour fuelled by the sighting this month of Ms Middleton's parents at a private shooting party at Balmoral, the precise timing of the announcement was successfully kept secret until the Press Association ran a single-line newsflash at 11.08am. The news then spread across cyberspace via the newly minted Twitter and Facebook pages of the British monarchy.

In a statement, Clarence House said Prince William had sought the permission of his fiancée's father, adding: "The Prince of Wales is delighted to announce the engagement of Prince William to Miss Catherine Middleton. The wedding will take place in the spring or summer of 2011, in London. Further details about the wedding day will be announced in due course."