So when exactly did Boris Johnson stop being our Mayor?

Perhaps it was around the time when the sitting MP for Uxbridge, John Randall, announced he was retiring – opening up a clear opportunity for Johnson to re-enter the Commons at next year’s general election, and thus stay in frontline politics having served his self-imposed limit of two terms as Mayor.

This means we are increasingly seeing Boris the PPC, Boris the prince-across-the-water for Tories who suspect they may need a new leader after May. What we don’t see much anymore is Johnson doing his day job – or at least one of them – being Mayor of London (of course, the £200,000-a-year Telegraph column gets filed every week).

To be fair, we do still see Boris at City Hall – but it’s clear he’s no longer batting for London very much. That would require views which are far too liberal, far too metropolitan; far too open to attacks from UKIP. Instead, his views now are firmly adjacent to the erogenous zones of the Shire Tories.

After all, a Mayor thinking about what London needs wouldn’t suddenly turn into immigration-bashing Eurosceptic.

Only last year, he risked the wrath of Theresa May and Tory MPs by criticising the Government’s tightening of visa controls for foreign students.  Now, he argues that UKIP has a point and that restricting the freedom of movement we enjoy through EU membership – and thus limiting both the influx of talent, and the opportunities Brits can and do exploit – is the only way forward.

But London faces greater challenges than ever before and needs a Mayor with their eye on the ball.

Last week, we found out that Johnson isn’t too bothered about the capital’s single most pressing issue – housing.

Under some dogged probing by Labour AM Tom Copley, the Mayor appeared to accept that he will not hit his target to build 55,000 new affordable homes by March 2015.

As of September this year Johnson had only delivered 38,412 affordable homes. When asked when the 55,000 would be completed the Mayor simply said “well I don’t know, whenever we’ve done them.” A clear sign of how seriously he takes the issue when millions of Londoners are crying out for more affordable and social housing.

Or take public health, for another example, with one of our Olympic boroughs having the worst incidence of TB in the western world. Newham has 108 cases per 100,000 people – more than twice the rate in India.

Then there’s child poverty. New figures from the Campaign to End Child Poverty show that London contains 14 out of the top 20 local authorities with the highest rates of child poverty across the UK.

All these policy challenges aside, there is even more at stake right now.  There’s a constitutional land-grab going on here, with plans for a new transport body for the north being announced by the Tories, and Parliament obsessing about ‘English votes for English laws’ – the wrong answer to the wrong question.

Yesterday, the Centre for London published a Manifesto for London which sets out an ambitious vision for a sweeping range of new powers, notably over tax revenue, as well as education, housing and welfare.

True, Johnson has called for negotiations on the back of this report, but why isn’t he leading the debate?

Labour’s Welsh leader Carwyn Jones was straight out of the blocks after the Scottish referendum, demanding more powers and fairer fiscal settlement for his own devolved administration.

Our Mayor, in contrast, has singularly failed to seize the opportunity for London, and we risk falling behind competitors like Paris and New York who already have more autonomy and power than us.  This isn’t just a problem for the eight million who live here, it’s a problem for the UK economy.

Johnson needs to remember who he was elected to serve; Labour can’t allow him to let this political moment pass London by.