Where Davies got the Glowing Sonic Screwdriver

I suddenly drew a connection the other day... In the new Doctor Who series, the Doctor's sonic screwdriver glows blue when in use. That isn't, however, the first time a sonic screwdriver which glows has been used - in 1996 Tom Baker came to New Zealand and recorded some adverts here (The results of which can be downloaded from my Doctor Who page). The longer of the five adverts featured the use of the sonic screwdriver, which as you can see below (just) emitted a beam of green light...

I win a prize for Ultimate Geekery!