[3][4][5] Rumbles was born in South Shields in England and was educated at St James School in Hebburn, County Durham, Sunderland Polytechnic where he graduated with a BEd, and Royal Military Academy Sandhurst.

Following the Scottish Parliament's establishment in 1999, Rumbles was Convenor of the Standards Committee when it was charged with investigating the so-called 'Lobbygate' scandal, in which the son of the then Secretary of State for Scotland John Reid was embroiled.

[8] On 12 May 2005, Rumbles announced his intention to stand for the vacant post of leader of the Scottish Liberal Democrats.

In particular, he specified a number of 'deal-breakers' for any coalition negotiations that might occur in the aftermath of the 2007 Scottish Parliament elections, with an absolute insistence on the implementation of key Liberal Democrat policies such as abolition of the council tax, and an enhancement of the Scottish Parliament's powers.

On 2 July 2008, following Stephen's surprise resignation as leader, Rumbles again announced his intention to stand for the Scottish Liberal Democrat leadership.