London Briefing/Chris Johns Global warming gets the blame for lots of things these days. In the UK, we have been told recently that rising global temperatures is the cause of a rise in the incidence of hay fever. It can't be long before the woes of the London Underground system will be laid at the door of those who drive SUVs.

Indeed, the sandal wearers missed a trick recently when Tube maintenance company Metronet blamed a heatwave for the decision to introduce speed restrictions on some key stretches of the tracks. Surely somebody could have laid the blame at the door of capitalism, globalisation and carbon emissions?

Metronet is a consortium comprising Atkins, Balfour Beatty, Bombardier Transportation, EDF and Thames Water. Metronet and another maintenance company, Tube Lines, are the proud recipients of 30-year contracts worth a reported £15 billion (€22 billion) to maintain and upgrade the creaking infrastructure that comprises the London Underground railway system.

These contracts were originally awarded in 2003 amidst great controversy and represented a defeat for Mayor Ken Livingstone in a long-running battle with central government. The "public private partnership" (PPP) deal that gave rise to organisations such as Metronet has already generated considerable disappointment, not least for the people actually running London Transport.

Last year, for example, some members of the London Assembly claimed that the public private partnership was failing miserably, following news that some of them had been fined large sums for failing to meet targets. Some stories suggested that Metronet had been forced to pay out at least £2 million in fines.

Fans of the partnership pointed out that while some aspects of the business had fallen behind, some companies had been awarded bonuses for beating targets. But the detractors seem to have more ammunition, at least in the early years of the contracts.

The latest twist to what promises to be a very long running saga comes with the news that sunlight is causing some rails to expand. Given that it is called the Underground, some people might be puzzled by this. Of course, long stretches of the Tube are, in fact, over ground. And it is here, where the sun hits the rail, that we have problems.

According to London's transport commissioner, Metronet is supposed to maintain the lines such that the onset of summer does not cause any problems. This, on the face of it, does not seem an unreasonable expectation.

Routine maintenance is supposed to reduce the risk that metal rails do not buckle when sunshine raises the surface temperature to around 50 degrees centigrade.

Peter Hendy, the commissioner, has claimed that Londoners are "furious" about speed restrictions across buckle-threatened lines.

The BBC reported Hendy blaming it all on a "basic failure to carry out routine work". Metronet has apparently apologised and promised to complete the work by August when, presumably, autumn cooling will cause other unforeseen problems.

London Transport's only sanction is a possible £1 million fine and an appeal to the shareholders of the companies involved in the consortium.

For an organisation that is so young, Metronet has already established a formidable track record, if you will pardon the pun.

A company that it had sub-contracted to clean parts of the Underground system was summarily dismissed earlier this year after it had been found to be underpaying its workers. Apparently something like 400 cleaners were found to have been paid £5.05 an hour, instead of the agreed £5.50 an hour.

Metronet were not to blame for the actions of the firm in question and, in fairness, did act promptly to solve the issues. But questions of underlying managerial competence are inevitably raised, particularly for an organisation that already had so many critics.

It's still early days of course, and 30 years is a very long time. The companies involved in these kinds of partnership projects do deserve some sympathy: the system they are trying to renovate suffers from decades of under investment. They still have 27 years to make a go of it.

Based purely on wholly unreliable personal experience, we can at least say that things are not getting any worse, melting metal notwithstanding. Ultimately, the success of these kinds of public sector infrastructure projects seems to depend on the amount of public money available. Metronet is hardly in control of that.

Chris Johns is an investment strategist with Collins Stewart. All opinions are personal.