The devolution revolution is barely 18 months old. Many parts of the country won't even take on their full devolved powers until next year, when they elect their first metro mayors. And yet there is already a palpable sense that the agenda is stalling.

In the North East, Gateshead and Durham are putting the brakes on a devo deal. The North Midlands has been left in limbo by the defection of a handful of districts. No sooner had George Osborne announced his intention for an East Anglia deal than Cambridgeshire pulled out.

It is important not to overstate the case. For every troubled part of the country, there is another which has grabbed the opportunities of devolution.

Two years ago few of us would have put bets on Merseyside, the Tees Valley and the West of England signing up to devolved metro mayors. The progress has been remarkably rapid.

But there is a real danger that the momentum is being lost just at the moment when the window of opportunity for devolution is starting to close. Councils need to stop wrangling over the details of devolution and grab what they can while the getting is good.

The window of opportunity is bounded by George Osborne's tenure at the Treasury. Devolution is very much a personal project for the chancellor.

Recent political events have tarnished his authority and reduced his chances of becoming the next prime minister. It is not clear whether either his or David Cameron's successor will have the same passion for local economic growth.

Britain is a country where all the defaults are set to the centre. If the chancellor stops pushing for change, we could easily see a slow drift back to Whitehall.

What is going wrong? To some extent this is a question of local forces of inertia kicking in. In some parts of the country MPs are doing their best to undermine the deals.

From Liam Fox in the West of England to Nick Brown in the North East, parliamentarians seem to have worked out that metro mayors are a challenge to their personal power. Many councillors feel exactly the same way.

The chancellor's semi-imposed geographies are hampering progress in other parts of the country. In both the North Midlands and East Anglia, the Government has encouraged the creation of very large and complicated entities comprising as many as 22 authorities.

It was always going to be tricky to herd all of those cats into the devolution fold, especially with so many two-tier areas now being rocked by unitary debates.

The most dangerous problem of all is the belief in some places that if they just hold out for a bit longer a different deal will emerge. This goes against all the evidence to date, which tells us that George Osborne will insist on directly elected mayors, prefers larger to smaller geographies and has dwindling sums of money to fund the deals. Waiting for a better deal might easily mean no deal at all.

Of course, there are all sorts of problems with the Government's approach to devolution. Our traditional sense of good governance suggests devolution should happen according to a clear strategy, with every part of the country included, the public fully consulted, a clear constitutional settlement and some sense of fairness and rationality.

The current devolution process breaks every one of those conditions, but it also has the great virtue of actually making change happen in a way England has not seen in a generation.

By far the best response to the chancellor's imperfect devolution process is to take the deal and find ways to make it better.

Activists in Greater Manchester frequently point to the undemocratic way their city's deal was done and the combined authority has responded with a major focus on consultation.

The new metro mayors will inevitably be a work-in-progress. On current trends their huge mandates will be completely out of kilter with their weak powers and political constraints.

If central government is serious about mayors, the prime minister will need to call them in over the summer of 2017 and negotiate a new wave of devolved powers for them.

Today's councils are a bit like salmon swimming upstream. As long as they keep fighting against the river they can slowly get closer to their goal. The second they stop, the current of centralism will wash them back out to sea.

Simon Parker is director the New Local Government Network