The 29-year-old goalkeeper will be out of contract at the end of the season and will be leaving Championship club West Brom on a free transfer.
Johnstone has a number of suitors in the Premier League who are keen to snap him up for nothing at the end of the season as they spy a bargain.
But it has been claimed that Tottenham are now the favourites to do a deal to sign Johnstone in the next transfer window.
Johnstone is one of the goalkeepers Tottenham are looking at as they look to bring in a strong back-up for Hugo Lloris.
They are not planning to take up the option on Italian goalkeeper Pierluigi Gollini’s loan and will bring in someone new.
Johnstone is a goalkeeper they like and his contractual status also works for Tottenham given he will be available on a free transfer.
It will leave Fabio Paratici with further funds to strengthen other areas of Antonio Conte’s squad ahead of next season.
The West Brom goalkeeper is keen to return to the Premier League after spending the last few seasons in the Championship.
