A HELICOPTER pilot who had flown many missions with both of the region's air ambulance services did not deliberately breach air clearance rules when he clipped a crane causing a fatal crash.

An inquest heard, however, that 50-year-old Peter Barnes had lost 'situational awareness' when his helicopter hit a crane at The Tower in St George Wharf, Vauxhall, south London, and plunged into Wandsworth Road on the morning of January 16 2013.

Mr Barnes - who had previously flown with the Yorkshire Air Ambulance and Great North Air Ambulance Service - was killed along with pedestrian Matthew Wood, 39, of Sutton, Surrey. Twelve other people on the ground were injured.

The father-of-two, who had 25 years of flying experience, was contending with poor visibility and freezing fog while flying from Redhill Aerodrome in Surrey to Elstree in Hertfordshire, when he was diverted to Battersea heliport.

Air Accidents Investigation Branch (AAIB) inspector Geraint Herbert told Southwark Coroner's Court it was difficult for pilots to map all such obstacles around London as identified in Notices to Airmen (NOTAMS).

NOTAMS gives only a general radius within which a potential hazard is located rather than an exact GPS co-ordinate.

"You don't know exactly where these obstacles are ... you have to plot the circle, and then all the other circles (on the map)," said Mr Herbert.

The court heard the fluctuating workload of pilots included maintaining a 500ft clearance from any obstacles. Some were mapped while others required visual identification.

Air traffic controllers directed Mr Barnes, from Berkshire, to a holding zone between Vauxhall and Westminster bridges while seeking permission from Battersea to divert him.

Mr Herbert said he did not take the most direct route but the final movements of the twin-engine Augusta Westland 109 helicopter might have been because he was avoiding patches of bad weather, but they also meant Mr Barnes had entered a restricted area.

The court heard cloud cover was around 700ft, the same altitude as the top of the crane.

Mr Herbert said: "We did conclude that he probably was not aware of his proximity to the building at the time he turned."

Mr Barnes's failure to observe the 500ft rule was not deliberate but "a consequence of this loss of situational awareness", the AAIB investigation concluded.

Air traffic controllers would not have been aware of the position of the crane, and it was the pilot's responsibility to avoid obstacles and inform controllers if he or she was unable to fulfil the required clearances.

Mr Herbert said Mr Barnes was required to remain clear of cloud, but it was likely he did not see the building just before the crash.

"Even when he was actually clear of cloud, because of the nature of the cloud ... his horizontal visibility might have been restricted in one direction, even though it might have been good in another direction."