London exploding pavements surge prompts death fears
Londoners are at risk of being killed in one of the increasing number of pavement explosions in the capital, the Health and Safety Executive (HSE) fears.
Figures obtained by BBC London show reported incidents of underground explosions more than tripled between 2011 and 2012.
In 2010, there were 12 underground explosions reported to the HSE.
Although that fell to eight in 2011, last year the figure jumped to 29. So far this year, there have been 12 blasts.
UK Power Networks, which distributes electricity in London, says it has increased inspections and is making a significant investment in testing underground equipment.
No-one has died as a result of previous blasts but John Steed, principal specialist electrical inspector at the HSE, warned that a fatality could happen.
Asked if he was concerned someone could die in a future explosion, he said: "It is my concern, yes.
"That's why I'm having regular meetings with UK Power Networks. I'm testing them. It's their risk."
Colin Wingate, 76, spent three months in a wheelchair with severe leg injuries after a pavement exploded in Harrow, north-west London, in August 2011.
"There was a huge - and when I say huge I mean enormous - explosion," he said.
"Huge to the point that the iron manhole cover left the ground, I left the ground - and it was Bedlam."
UK Power Networks accepted liability more than a year after the blast which left Mr Wingate injured.
He added: "They are not doing enough to ensure that these accidents, incidents, call them what you like, don't happen anymore.
"Because sooner or later, at the rate these explosions are continuing, someone is going to lose their life."
The blasts can be caused by an electrical fault, often when water has seeped into cables, or by a gas leak which has been ignited by a spark underground, UK Power Networks said.
The force of the explosions can surge up and dislodge manhole covers.
In April, mobile phone footage captured a large explosion from beneath a pavement in Pimlico in south London with a pedestrian a few feet away.
In May 2012, three women were injured when a cable pit - or manhole cover - blew up in Edgware Road, central London. One woman was badly burned and received what police described as "life-changing injuries".
The following month, a woman received whiplash injuries in St John's Way, north London, when an underground electrical link box exploded.
The HSE investigated and subsequently issued an Improvement Notice to UK Power Networks for failing to report a fault it knew about 12 months earlier.
Mr Steed said: "Worse than that, on the day that it blew up they actually sent some staff out to do some testing work at fault locations, including that box itself. So they put their own staff at risk. "
Matt Rudling, director of customer services at UK Power Networks, said there had been very few incidents where the fault had had an impact above the pavement, and they should be placed in context.
"We have about 100,000 boxes in the pavements of London and about 36,000km of underground cable," he said.
"We have relatively few cases when our equipment has faltered.
"Sometimes that's due to other parties coming into contact with our equipment.
"For example, someone may be digging the street, sometimes water can gain access into our equipment, fortunately these are very rare but they will cause our equipment to fail."
Mr Rudling said the company was investing about £40m over the next eight years to ensure London's electricity supply remained "safe and reliable".
The HSE is still investigating many of the recent explosions, but believes the unusually wet weather in 2012 could be the cause. It has asked UK Power Networks to do further testing on its underground equipment.
Tony Cohen, the firm's head of London operations, said four teams were inspecting about 80 cable pits every day in London.
He said: "I'd like to assure people in London that it's [explosions] very, very rare.
"I'm a Londoner, I walk through London every day and they shouldn't be concerned about it."