It was just a throwaway line in Gordon Brown's excruciatingly prolix Budget speech, but its impact on contractors may be immense.
In passing, the chancellor mentioned increasing the number of permits issued to overseas workers. The total number, say Whitehall sources, is likely to be 20,000 – one-quarter of the extra staff construction needs by 2006.

Brown's off-hand endorsement, though, belies 18 months of wrangling between the DTI – which has always wanted to relax curbs on immigration – and the Home Office. David Blunkett's department was reluctant to acquiesce, fearing that any downturn in construction would mean an army of social security claimants and some headlines in the Daily Mail. It might still, given the implosion of the commercial market. But at least the government has helped the industry along as it scrambles to spend Blair's billions on schools and hospitals. BAA, meanwhile, is sufficiently worried about shortages to have held talks with a refugee agency to find hundreds of workers for Terminal 5. And look at what they're offering …

Brown's statement suggests that the DTI has got its way, although the work permits may be of limited duration and restricted to those with the equivalent of five GCSEs. Nonetheless, it's the most visible sign yet that the government is softening its line on immigration. It follows the Home Office's decision to allow a recruitment agency to offer visas to Romanian workers, and the comment from immigration (and former construction) minister Beverley Hughes that a "fortress Britain" would damage our position "as a strong global economy".

Construction's need for immigrants is not just a numbers game; it's also a question of heritage. Like the catering trade - which will get another 10,000 permits - construction was founded on immigration. And neither could survive without skilled foreign workers. Nearly one-third of the builders of Paternoster Square, next to St Paul's, are from overseas, like the Hungarian cladding fixer we interviewed, or the Italian site manager (pages 36-39). Cynics will argue that British workers might have performed both roles – except they'd have wanted more money. But, as developer Peter Rogers points out, foreign workers have specialist skills that their British counterparts no longer possess. And, more than that, life on site just wouldn't be the same without ethnic diversity. Listening to Janos and Severio, you realise what contribution they make to the buzzing, cosmopolitan communities behind the hoardings.

There has always been a casual snobbery about the way governments embraced doctors and teachers from overseas, but repelled site workers. Now is the time to end that iniquity. While Brown also mentioned that he'd combat illegal immigration, he must know he'll never eradicate it. Better to get them in the white economy and grab the tax revenue (heaven knows, he needs it).

The cornerstone of policy must be flexibility. Not all of the work permits can be open-ended; indeed, many workers don't want them to be. They want to travel. But for those who stay, there should be life-long permits, decent wages, safety training and health screening. If they invest their time, sweat and skill, they should get the dividends. They are, after all, the indispensables.