Apparently, since 2001 there have been three seizure of dope in the House of Commons since 2001, two of which were in 2005 and the other in 2006. The pot in all circumsatnces was apparently of a quantity "consistent with personal use"
This means that it was during the time of Charles Clarke's tenure at the Home Office. Some may recall that during that time briefings often floated the idea that what should be considered "personal use" rather than "intent to supply" should be raised. As such, the seizure could be anything from a sixteenth to twenty ounces*.
I wonder who the potheads were? Researchers perhaps, or MPs? If anyone knows do share the information with me!
* A lot of pot. Enough to keep a healthy student flat going for at least six months.