On May 1 1997 bristling with energy the 44-year-old Tony Blair rode into Downing Street on a wave of optimism Britain hadn't known for years.With the Labour Party anthem of Things Can Only Get Better ringing in his ears Mr Blair pledged social justice and "whiter than white" ethical standards, while inviting rock stars for drinks at Number Ten as the age of Cool Britannia began.Far removed from the Euro scepticism of the previous Conservative regime, Mr Blair's arrival heralded a promise that Britain would play a full part in the development of the EU and form greater relations with our European neighbours.The future still looked bright as the Blairs celebrated the new millennium hands linked with the Queen, as fireworks lit up the London skyline. However, one moment was to change everything.When in 2001 the tragedy of September 11 hit New York the course of the Blair years was set to change. His instinct to support the US became caught up in a much wider shift that saw Britain's foreign and defence policies swing into alignment with George Bush and Washington.It was a defining moment that shaped the rest of his premiership. The attack was seen as part of a wider global terrorism threat that needed to be crushed. The 'War on Terror' became a war in Iraq, a move that was hugely controversial in Britain.As Mr Blair's reign became tarnished by bloodshed in Iraq other controversies loomed. Significantly he had to suffer the indignity of becoming the first serving Prime Minister to be interviewed by detectives investigating the alleged sale of political honours in exchange for donations to party funds.Politically wounded, it appeared that Mr Blair was slowly being forced to surrender influence to his long-time rival Gordon Brown. Claims of bitter arguments and grudges between the two men became common, with rumours suggesting that at one point they had stopped talking to each other.When he announced last summer that the autumn party conference would be his last as leader, few were surprised. Indeed some commentators said he looked almost relieved when he took to the podium and acknowledged it was time to "let go".Considering many of the troubles that have blighted his last few years it will surely have pleased Mr Blair that his final days have been filled with optimism. Standing next to Northern Ireland's newly sworn in First Minister and DUP leader Ian Paisley and Sinn Fein's Martin McGuinness at Stormont, peace in Northern Ireland has seemingly been secured.That note of optimism harks back to 1997, but only time will tell whether historians look back on the Blair years fondly or if they will be overshadowed by Iraq. What is for sure is that Mr Blair will want history to remember, as he said in his resignation speech, that he "did what [he] thought was right for our country."© Independent Television News Limited 2007. All rights reserved.