McClelland, the chief coach, took temporary command following the recent sacking of Alex Totten - and now he will be assisted by Harrison as well as Ray Stewart. 'They will be in charge of all team affairs at St Johnstone for the remainder of the season,' a club official said last night.
Harrison, a player with Blackpool, Vancouver Whitecaps, Watford and Charlton, was coaching at Watford under Graham Taylor when McClelland was a player there.
He followed Taylor to Aston Villa and also joined up with him again on the international front. That ended in ignominy, however, when Harrison's duties were terminated following a distasteful prank that saw him sacked by Millwall.
The pair face a stiff test today - against the champions, Rangers, at Ibrox. McClelland said: 'Of course Ibrox creates pressure because of the crowd and the intimidating atmosphere, but surely that's what professional football is all about. I want players who revel in playing at places like Ibrox.'
McClelland is unlikely to alter his line-up but Rangers look certain to have Richard Gough back in defence after injury. Also fit again is Trevor Steven but the midfielder, Ian Ferguson, starts a two-game ban.
Celtic, lying third, take on fourth-placed Hearts at Tynecastle. Celtic will have Tony Mowbray back after suspension while Brian O'Neil has recovered from a groin injury.
Hearts retain Nicky Walker in goal, Derek Ferguson is doubtful and Ian Baird is suspended. The Hearts manager, Joe Jordan, has secured the former Bristol Rovers defender, Adrian Boothroyd, on an 18-month contract and he is likely to figure today.
Aberdeen, at home to Hibernian, will be without their top scorer, Duncan Shearer, until the new year as he recovers from minor knee surgery. Scott Booth and Eoin Jess continue up front.