An update for the 21st Century based on old Cockney rhyming slang. See Guy Ritchies 'Lock Stock and Two Smoking Barrels'.
It rhymes with wank so can either be used to mean having a wank- or a Barclay's Bank in old Cockney rhyming slang. I'm just going for a quick Tom to relieve the stresses of the day.
Or it can mean something is not very good. As below
ME- 'Clarence did you see the Coldplay Concert last night?'
CLARENCE- 'Yeah, I did but it was a load of old Tom Hank from start to finish, basically as soon as the band started playing.'