An added incentive is the enhanced rate of pay on offer. Typically, NQTs working on supply can expect to earn 0. 4 or 0.5 on the spinal points compared to 0.2 for a first staff job. Maggie Taylor, of Capstan, says her agency is now signing up young people straight out of teacher training college: "A lot of them do day-to-day supply teaching. It enables them to get a wide variety of experience so that they stand a better chance of gaining a permanent position."
Chris King, director of education for Timeplan, the UK's largest teaching supply agency, is actively recruiting NQTs at trade fairs and on the university milk round much as local authorities used to.
"Over the past few years we have discovered increasing numbers of young teachers who are unwilling to come to London and take up a permanent post and go into a school that could be the school from hell," he says. "They are playing the field instead."
Mr King, who came to London "from the sticks" himself in the early Seventies and taught for 20 years in Southwark and Hackney, says the capital doesn't hold the attraction it once did for young teachers looking for a first job. "We have to try to bring young teachers into London. They don't always want to commit themselves to a long-term post but if you say to them 'why don't you come and give it a try' you get a very different response." He believes this 'suck it and see' approach could be a solution to the shortages in the capital.
"There isn't a shortage in other parts of the country. They say 'what shortage?'. What we have is a regional shortage and it is greatest in London and the South-east. The situation in London is such that we have to come up with as many alternative ways of recruiting as possible."
Rather than creating a new breed of itinerant career teachers, he believes the increasing use of agencies by NQTs is symptomatic of the ever-more flexible labour market (they have got more choice and they are exercising that choice) and makes them more willing to consider working in so- called "difficult" schools if they know they have a get-out clause. "But we have had people go into very difficult London secondary schools who found that they fitted in and ultimately they have decided to stay. "
In January this year, 20 out of the 22 local authorities which had teacher vacancy rates of over 1 per cent were in London. Even in primary schools, where shortages are less pronounced than in the secondary sector, vacancies in the capital had doubled in two years, accounting for one third of all unfilled posts in England and Wales.
In Tower Hamlets, one of the three boroughs along with Newham and Barking,which was finding it hardest to attract staff, things have not improved.
"We are finding it quite difficult to recruit," said Helen Bakaszynsky of the borough's primary pool recruitment team. "We had about 20 vacancies still not filled by September out of our target of 55."
Finding the staff has been getting much harder and reminds her of the last great recruitment crisis of eight years ago. "We want to do all we can to make sure that doesn't happen. There are a lot of preconceptions about how difficult it is working in London but people don't always appreciate how much support they actually get."
John Howson, an expert in teacher supply and fellow of Oxford Brookes University, says the "Hackney factor" - bad publicity surrounding the poor showing of certain boroughs - might not necessarily be to blame for the lack of interest in inner-city posts.
"That can work both ways. If you are in the news and you can show you are doing something about it then there may be people who would like the challenge of working in those schools. "
Instead, he thinks the shortfall in teaching staff is more to do with the growth of FE and universities (attracting people who might otherwise have become teachers to stay in higher education) and with the economy picking up, more people are leaving their career choices until later, and then plumping for something other than teaching.