Alex Salmond was one of the great politicians of his age. His impact, not only on ­Scottish politics, but those of the entire United Kingdom, cannot be ­overstated. And he was my friend.He and I entered Parliament together in 1987, Alex as the SNP member for Banff and Buchan and me as the ­member for Boothferry in Yorkshire.Over the course of the next 23 years we had our fair share of disagreements, and our views often differed dramatically. Nevertheless we became firm friends. He possessed a fierce intellect and I enjoyed many evenings sparring with him.His training as an economist meant that I had a proper fight on my hands when we debated some of the issues of the age. And between us we undoubtedly drank too much whisky and too much wine in those sessions.Indeed, he seemed to have infinite stamina and little need for sleep. Alex Salmond and David Davis became close friends after both entered Parliament in 1987Within just four years of him gaining election to Parliament, Alex had already pushed on to secure the leadership of the SNP and it was under his leadership that this minority group transformed into a formidable force in Scottish politics.After the referendum, we were back in the Commons together again, typically, but not always, on opposite sides. We did the interview rounds on the night of the EU referendum, on opposite sides of course, but the most notable ­feature of the evening was the frustration of the interviewers when we were able to forecast almost exactly what the outcome would be after only a few results.Alex would tease me that I could have got much better odds on my bet on winning through the night. Sometimes we were squarely on the same side. On the Iraq War, for example, we were co-signatories of a motion summoning Tony Blair before the House of ­Commons after the Chilcot Inquiry.It was the only thing that ­Theresa May asked me to reverse when I entered Cabinet, so Alex had ­maintained his ability to get me into trouble.He resigned from the SNP in 2018 in the face of sexual misconduct allegations about his time when he was First Minister.It was, in the words of Fergus Ewing, the ‘scandal of our age’. Yet, in the end, Alex was ­vindicated.The Court of Session ruled that the Scottish Government’s ­handling of complaints against him had been unlawful and that it had engaged in a ­process tainted by bias against him.After such bruising legal battles, many would have understood if Alex had called it a day, knowing he had already changed the face of Scottish politics.But, in 2021, he again entered the political arena, joining the newly created Alba Party as their leader.He and I worked closely in recent years. I was frankly very angry about his treatment, and I used the privilege of the House of Commons to expose some of the deceits and encourage ­Holyrood to reveal the grotesque misbehaviour of the Scottish Government.Perhaps my fondest memory was the ten days we spent together at the Edinburgh Festival, in the series of debates The Ayes Have It – it was a delightful and charming experience, I think for everybody, and it will live on in my memory of him.His death came a day before I was due to meet with him to ­discuss the next round in dealing with both the Scottish Government’s malevolent actions against him and the failure of the rule of law in Scotland.I will, in his memory, ­continue the battle to ensure that ­justice is done. And it will be Alex ­Salmond’s ­victory when we achieve the ­protection of privilege for the Scottish parliament, when we get proper separation of powers between the Executive and the Scottish judicial process, and when we force a duty of candour for the first time on the Scottish Government.Lots of politicians are driven by events. Not Alex. He was a man who drove the events, and he still will after he is gone.His life is a testament to his unwavering belief in the right of the Scottish people to determine their own destiny.He will be greatly missed, and Scottish politics will be much worse off without his towering presence.