The sapphire-blue dress worn by Kate Middleton on the announcement of her engagement to Prince William has flown off the shelves and is already sold out in boutiques and department stores in London.

The dress, by Brazilian designer Daniella Issa Helayel, comes with a price tag of 399 pounds (638 dollars). It was described as being part of the core range of dresses sold under the Issa label, which is hugely popular with celebrities including Madonna, Kate Moss, Kylie Minogue and Scarlett Johansson, reported The Times.

In Middleton’s case, it matched the sapphire and diamond engagement ring she was given by Prince William, which once belonged to his mother, the late Princess Diana.

Two days after the couple announced that they would marry next year, the souvenier industry has already gone into overdrive.

Sales of a lookalike royal engagement ring, offered at around 35 pounds, rocketed overnight as the production of memorabilia mugs and plates went full steam ahead — even though the wedding date is not yet known.