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After four months of haggling, the 184-year-old firm of John Mowlem & Son, builder of the NatWest Tower, Somerset House and London Bridge, is to be subsumed into Carillion. Apart from the passing of an era, the £313m deal creates a £4bn-turnover player to rival Balfour Beatty.

But the success of the new entity is not a foregone conclusion. John McDonough has spent five years turning Carillion, a muddy-booted contractor, into a sleek, services-focused, City-friendly business.

On the credit side, the deal is being showered with goodwill from clients and the City. And in a world where contracts are getting bigger, and most contractors are forced to enter into unwieldy joint ventures to handle them, Carillion should now enjoy a competitive advantage.

The drawback is that in buying Mowlem, a good traditional company that lost its way, McDonough has arguably gone two steps backwards. If he wants to keep a fickle City happy he'll need to go four steps forward, and quickly. Hence the redrawn corporate structure, headed largely by Carillion executives. These people will need all the managerial guile they can muster to galvanize Mowlem's demoralised staff, who've had a pretty torrid time of it, and fuse the two cultures. And he will need to quickly decide on what to do with awkward parts of the business, such as the Barclay Mowlem arm in Australia. And then there are the inevitable questions about whether Carillion ended up paying too much to outbid Balfour Beatty, and whether its due diligence was really diligent enough.

So the deal is still a gamble for McDonough - but its also shows chutzpah and vision. In fact, it's not too far removed from the ambition shown by John Mowlem, the Swanage stonemason, who crafted Nelson's tomb at St Paul's Cathedral before going on to found the eponymous business.

The story of us

Construction workers have always been gifted commentators. Take, for example, the site workers who spend entire days talking in the voices of invented characters - the genesis of some of the grotesques invented by Paul Whitehouse in his plastering days. Then there are the site managers who can express their feelings about a delayed load of doorsets in terms that would make a pirate blush. So far, the public has been largely sheltered from the industry's collective stream of consciousness. But for how much longer? In the States the craze for keeping online diaries, aka web logs, aka blogs, has reached their construction industry, and the results make for interesting reading. How will our industry take up the challenge? Will clients find out what their suppliers really think about them? Will a mass debate spring up on sustainability? Will your partner find out what you got up to at MIPIM?