Apparently from the Holy Moly weekly email:
John Barrowman (Captain Jack) was signing memorabilia at a Doctor Who convention last year when a fan reached the front of the queue.
"Will you sign this please?" he said and presented Jack with a large dildo, engraved with this scene from the WWII story of Jack sitting atop a German bomb.
"My wife uses it on me," said the fan helpfully. Ever the gent, John signed it.
John is famous in what the tabloids refer to as "gay circles" for having a large knob, somewhat akin to a length of dirty skipping rope. This pales in comparison to his boyfriend, however, who has one like a leg of lamb with a hole drilled in the top. Captain Slack?