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A tale of two sentences, drafted in two different capitals, exposes the clear blue water between London and Brussels.

In Theresa May's letter triggering Article 50 of the Lisbon Treaty she states: "We believe its necessary to agree the terms of our future partnership alongside those of our withdrawal from the EU.'

But Donald Tusk responded today: "Starting parallel talks on all issues at the same time as suggested by some in the UK will not happen."

Bluntly, the divorce bill would have to settled before talks on trade can begin.

What's more, only one party to the break-up, the European Council, would decide if the settlement is good enough.

This rebuff was always likely, and the Downing Street response restrained - in effect, reminding us we were simply at the beginning of the negotiating process.

So no flames fanned, but it may not be long until Theresa May feels the heat.

Ahead of a divided Labour Party in the polls, she may be at the zenith of her political popularity.

Because now her own party's apparent unity is set to be tested.

If some of her own MPs don't like the size of any proposed financial settlement, they may not only suggest it's better to walk away with no deal, but attempt to apply pressure to this end.

That in turn might lead to the largely self-muting Remainers in her ranks to find their voice.

And there are more time bombs in Tusk's draft guidelines.

If Theresa May wants a transitional deal, she will have to accept a "supervisory" regime for a time - presumably the European Court of Justice whose jurisdiction she wants to end.

So UKIP are likely to claim by the next election that we are still "half-in, half out".

And with the EU refusing to do a final trade deal until after the UK has left, it may be difficult for her to demonstrate the benefits of leaving - allowing the Liberal Democrats to claim we should never have cast aside single market membership in the first place.

It's an old political adage but one with which Theresa May will be familiar: "you cannot please all of the people all of the time."

But she may find it a challenge to please some of the people some of the time, even in her own party.