was 1.055 and Whitbread IPA was a bottled beer of 1.036 and 3.7% (compared to their standard X Mild at 1.042 and their draught bitter at 1.042). Greene King IPA (3.7%) and Charles Wells Eagle IPA (3.6%) are examples of IPAs in this tradition. Worthington's White Shield is an example of a historic India Pale Ale, first brewed in 1829 principally for export to the British Empire. By the 1960s White Shield had become a cult drink brewed in small quantities for a dedicated following, but it found renewed popularity in the early 1970s when the demand for real ale grew in the UK. The revival of IPA in modern times dates to a seminar on Burton pale ales organised by publican Mark Dorber at his pub, the White Horse, Parson's Green, in 1990. That led to a pale ale festival in 1992 and an IPA festival in 1993, for which Bass brewed a 7.2% beer inspired by Bass Continental, originally brewed for the Belgian market before World War II and based on Bass recipes going back to the 1850s. Dorber and Roger Protz then organised an IPA conference in 1994 at Whitbread's brewery in London, attended by brewers from both sides of the Atlantic. The influence of this meeting persists, for instance Brooklyn Brewery's East India IPA is based on the beer that Garrett Oliver took there. In the 21st century, US-influenced IPA is one of the most popular beer styles in the UK. In 2019, Brewdog's Punk IPA was the country's best selling craft beer in the on-trade and Swannay's Muckle IPA won overall craft keg gold in SIBA's Independent Beer Awards. United States In the late 20th century craft beer revolution in the United States, brewers began seeking out old beer styles that had fallen out of vogue; Ballantine IPA, which had been made in the U.S. since 1890 until the 1990s, proved inspirational. The traditional IPA style was well-suited to model the intense flavour and aroma of American hops. Bert Grant of Yakima Brewing and Malting identified that Cascade and Chinook hops, grown locally in Yakima, Washington, provided strong flavours when showcased in an IPA. The boom in popularity for IPA as a style spread down the west coast of the United States, then across the United States and eventually the world. It is estimated that over 40% of craft beer brewed in the United States