Accident on West End Lane

Anyone using West End Lane between about 8 and 9 this morning will have noticed the very large tail back and unusually heavy queueing.  I suspect many people will have thought that Thames Water must be back with their unending sewage works as the tailback went up as far as the dreaded Sager building.
Unfortunately, though, the cause was much more serious. What looked to me like a very nasty accident had caused the emergency services to close off the stretch of West End Lane between Iverson Road and Broadfield Gardens.  I'm not sure what had happened - but as I passed by the West Hampstead Overground station at 8:00am I saw two buses were pulled over and at least one person looking very seriously injured on the ground.  There were several police cars and paramedics on the scene.
I hope the person I saw injured is able to make a full recovery.