Hi Tac,I hate to contradict you but the pistol is a firearm. The Firearms Act defines a firearm as " a lethal barreled weapon of any description from which any shot, bullet or other missile can be discharged and includes any prohibited weapon etc etc "
As an ex Police Inspector, I can assure that if you robbed some one using an air pistol you would be charged with firearms offences.
It may not be a powder burner, but is a firearm!
Best regards,mcmj