A flash of ankle. A flutter of eyelashes. A glimpse of skin – really seen or imagined. Boris is doing his fan dance again.

The Sunday Times and the Sunday Telegraph both report that the Mayor will this week speak in support of a new report, published by his office, which suggests that London would do better outside the EU, with an outward-looking trade approach, than inside an unreformed European project. It’s a view that could be briefly summarised as “Better Off Out”.

Of course, Boris doesn’t make the full step. Here’s a ‘source close to Johnson’ in the Sunday Times:

“Boris favours a renegotiation in which we stay in and complete the common market,” the source said. “He believes that is achievable by being bold about that renegotiation and not having that fear about leaving. If voters say that’s not enough and we leave, the longer-term aspects of that are not as damaging as people might imagine.”

The Mayor’s charge that any renegotiation is fundamentally undermined if the Prime Minister goes into it saying he wants Britain to stay regardless is correct. Demands with no repercussions if they aren’t met are likely to be rejected (though the EU is in my view institutionally opposed to any meaningful renegotiation, and the Foreign Office has failed to produce proper demands anyway).

There have already been a few hints that Cameron’s earlier declarations that he would definitely vote ‘In’ in the 2017 referendum are weakening. Boris’ intervention will likely add pressure to that process.

But this is, inevitably, about more than just our membership of the EU. Just as the reshuffle’s Frustrated Five are seeking topics which will secure headlines and put pressure on the Prime Minister, so Johnson is in search of a way to keep his leadership options open. The failure of Cameron’s renegotiation strategy offers a prime opportunity, and he has taken it – doing so seems to have been an easier decision than settling on when and where to re-enter the Commons.

This is another sign that, should we lose the 2015 General Election, the subsequent leadership race will be won by a candidate willing to support British independence from the EU.

What Boris really thinks about the topic is a source of continued debate – flourishes like this are intended to imply he is an Outist, while his critics like Louise Mensch claim he is a fully-committed Europhile. But that’s the point of a fan dance – the performer shows just enough to hint, to titillate and to tease. Full exposure might disappoint the audience.