By Nick Higham BBC media correspondent

Slowly, ever so slowly, Carlton and Granada are creeping closer to a merger.

Cold Feet is made by Granada

You can see the process in two ways.

Either it's like the ending of one of those romantic movies in which the hero and heroine run towards each other in slow motion, arms outstretched, her blonde hair streaming in the sunlight.

Or it's like one of those slowed-down car safety videos where the crash dummy splinters as the car collides with the wall.

The Communications Bill going through Parliament now removes all the legal obstacles to the two companies merging and creating a single ITV.

There remain however some hurdles.

The biggest is probably the opposition of the advertising lobby.

Some, though not all, advertisers and their agencies object to a single company controlling more than half of all commercial television ad revenue in the UK.

Last week the proposed merger was duly referred to the Competition Commission, which will have to decide whether the advertisers' fears are justified and if so what to do about it.

Advertising

Cue many weeks of wrangling over whether Carlton and Granada are dominant players in the market, and what "the market" is.

Is it just the market for television airtime, or is it the market for advertising as a whole?

How far is television advertising "substitutable" by advertising in other media?

And how far is a campaign on a basket of digital channels, plus Channel 4 and Five, able to replicate what a campaign on ITV alone can deliver?

Publicly, Carlton and Granada profess not to be worried by the Competition Commission referral.

It's simply a question, Granada's chairman Charles Allen told a recent TV industry dinner, of devising a way to hive off some ITV airtime sales to a separate company.

Debacle

At the same dinner, asked whether ITV had abandoned its search for a network chief executive, Allen replied that he would be doing that job once the merger went through, with Carlton's Michael Green as chairman.

But that presupposes that both men, and their companies, are still around.

Both companies' share prices have fallen dramatically in the wake of the ITV Digital debacle, the advertising recession and the general share price slump.

Investors seem to have little confidence in either company's management.

One likely scenario is that outsiders may launch a takeover bid for one company or both before they get to the stage of merging themselves.

The lady with the streaming blonde hair may find herself tripped by a rival suitor before she reaches her lover's arms.

Or someone may put the brakes on before the crash dummy hits the wall.