IT seems unlikely but the Westminster government claims its new strategy on immigration is working.

It's the tactic where vans have been touring London with advertising hoardings declaring: "In the UK illegally? Go home or face arrest."

Just "text Home to 78070 for free advice and help with travel documents". And, very likely, a lift to the airport from the UK Border Agency.

According to Downing Street there has been a "great deal of interest" from illegal immigrants voluntarily calling a government helpline and asking how to leave the country. Among the rush will be families eager to return to some Taliban-ruled village where daughters seeking an education will be shot in the head. And what's a bit of persecution here or there when there is the opportunity to revisit some sunny African family homeland. Even if many of the family have been murdered or disappeared.

Eastern European illegals will happily give up the rent-free £1m council house, lavish benefits, the BMW 5 series car, and the wife's steady job selling the Big Issue to return to life in a wooden shed in a country whose name ends in stan. (Previous sentence may contain irony.)

But today's topic is not immigration. I am a woolly liberal on that subject. Something to do with the Shields family escaping 173 years ago from abject poverty in Donegal to relative poverty in Glasgow's Gorbals.

Today's topic is the efficacy of Government vans with big posters warning people about behavioural patterns. It might be more difficult to sleep soundly in your bed late of a morning if there is a large mobile message outside asking: "Having yet another duvet day, are we?"

The neighbour's enjoyment of such a spectacle may be ruined because the message can be changed electronically and instantly to: "And what are you daein hinging oot the windae, Mrs McGlumpher, when you've missed your last three turns at the stairs?"

If the Westminster Coalition has a spare advertising lorry they might park it outside Nick Clegg's house. Asking if maybe reneging on written election pledges about university tuition fees should be a resignation issue.

These mobile advertising campaigns might turn out to be as useful as the messages on motorway gantries. Such as Tiredness Can Kill. But you won't fall asleep for worrying that you didn't check your tyre pressures or you may not be a courteous driver.