Lawrence Simonini donned a prison officer’s uniform in a bid to look respectable as he drove north along the M6 and M74 from Liverpool.
Russell Baillie, the warden it belonged to, claimed he gave the uniform to Simonini to wear at a fancy dress party.
However, the jury at the High Court in Glasgow didn’t believe that story and Simonini (29) and Baillie (31), of Shotts, were convicted of being concered in the supply of amphetamine last month.
Undercover cops tracked the pair’s movements and Simonini’s hire car was stopped in March 2014.
Simonini claimed he knew nothing about drugs and thought he was bringing a load of fake jeans to Glasgow.
A third accused, Joshua Quinn (26), from Liverpool, was found guilty of being concerned in the supply of amphteamine in August 2013, on journeys between Renfrew, Larkhall and Paisley.