Bertie has rejoined Fianna Fáil - but what's his goal here? Journalist and commentator Lise Hand joins to look back over the rise and fall of Ahern, revisiting his role in the Mahon Tribunal, and we ask what happens now - could we see him make a run for president?The Explainer is brought to you by The Journal. Providing open access to valuable journalism in Ireland has been the aim of The Journal for a decade. You can contribute to ensure we can keep questioning, investigating, debunking, explaining and informing at www.thejournal.ie/contribute/