From the summary of the Chatham House report on Blair’s premiership:

As Tony Blair approaches the tenth anniversary of his election victory, and his final year in power, this paper assesses the impact of these, and other, events and concludes that a more nuanced relationship with the United States will be a requirement for Blair’s successor.

Although Tony Blair did not express much interest in foreign policy before becoming prime minister, in Labour’s first term it must be judged a qualified success. A key feature was Blair’s ability to demonstrate Britain’s European credentials while forging a close working relationship with President Clinton.

The post-9/11 decision to invade Iraq was a terrible mistake and the current débâcle will have policy repercussions for many years to come.

The root failure of Tony Blair’s foreign policy has been its inability to influence the Bush administration in any significant way despite the sacrifice – military, political and financial – that the United Kingdom has made.

Tony Blair’s successor(s) will not be able to offer unconditional support for US initiatives in foreign policy and a rebalancing of the UK’s foreign policy between the US and Europe will have to take place.

Full report here.