As politics returns after the August hiatus, pro-Europeans should view the state of the Brexit process with equal measures of concern and optimism.

Concern, because it is increasingly clear that the negotiations between the UK government and the European Commission are sinking into a quagmire, with increasing bad blood on both sides.

And optimism because there are real signs that effective opposition to the course charted by the government is growing, especially in the Labour Party.

The most significant development of recent weeks has been Labour’s shift in stance on single market and customs union membership.

Previously, Labour’s position, if it could be articulated, was difficult to distinguish from that of the Conservatives, which meant that there was very little significant political and parliamentary pressure