Johnstone made 167 appearances for West Brom after arriving from Manchester United for £6.5m in 2018
England goalkeeper Sam Johnstone is close to joining Crystal Palace.
Johnstone is out of contract at West Brom at the end of the month and has already told the Baggies he will not be staying at the Championship club.
A number of clubs have been interested in the 29-year-old, with West Ham particularly keen last season.
However, it is understood Palace are now at the head of the queue, with Johnstone set to become Patrick Vieira's first signing of the summer.
Johnstone's arrival is likely to trigger the departure of Jack Butland from Selhurst Park.
Butland, who was capped by England nine times between 2012 and 2018, has struggled to make an impact at Palace, where the 29-year-old has largely been second choice to Spaniard Vicente Guaita.
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Source: bbc.com