It's long been said among those who know him best that Prime Minister Stephen Harper has terrific sense of humour, though it is seldom seen in public.

On Wednesday, amid the political storm surrounding Harper due to questions around Senate expenses and the decision by an MP to leave the Conservative Party caucus over transparency and accountability issues, a video surfaced showing the PM’s lighthearted, humorous side.

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The video, uploaded to YouTube Wednesday by “Steve Harper,” appears to have been shot on May 3, 2011, the night Harper’s Conservatives won their first majority government, as the PM conducted a sound check at his election night headquarters in Calgary.

The normally businesslike Harper stands at the microphone grinning and begins doing impression of previous leaders while his wife Laureen and son Benjamin urge him to just "read the speech."

He ignores their entreaties, instead mimicking Joe Clark, Brian Mulroney and Preston Manning, often laughing at his own jokes, walking away from the mic then going back for more.

"I do them all, I do them all," he says at one point, as Ben puts his arm around his dad and tries to pull him away from the podium, saying: "You're done! You're just too clever dad."

When Harper finally leaves the stage and the camera pans back, Sen. Marjory LeBreton can be seen in the crowd, laughing and apparently wiping tears from her face.

Harper is currently in England, but has recently faced tough question from the opposition in the House of Commons over a cheque written by his former chief of staff Nigel Wright to help Sen. Mike Duffy pay off improper housing expenses.

And one of his backbench MPs, Brent Rathgeber, resigned from caucus last week over concerns about the government's approach to accountability and transparency, and said too much power has been delegated to the Prime Minister's Office.