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A pair of outdoor swimming enthusiasts have documented the humble beginnings and enduring appeal of Britain's lidos.
Janet Wilkinson and Emma Pusill visited more than 100 outdoor pools because of their "passion" for lidos and public swimming.
Their book, The Lido Guide, features pools across the UK, including those in Lincolnshire, Sussex, Essex and Wales.
Historic Pools of Britain said outdoor swimming "has seen a big revival in recent years".
"Many lidos have been lost, but an increasing number are being rescued and there are active campaigns to rescue even more," said Ms Wilkinson.
"We love the sense of community, the beauty of sunshine through water, the companionable solitude of the swim and the chat with other swimmers that seems to flow so much more readily when not constrained by a roof.
"And we love the cafes, tuck shops and cakes that so often go hand in hand with lidos."