You have given limited information but based on your limited info below, it appears they were going to work through a new turnstile (which I assume is on company property) and the person fractured there ankle?
It is irrelevant whether the job was notifiable (F10) or how long it has/had been open.
It is notifiable to the HSE:
Fractures, other than to fingers, thumbs and toes
Bone fractures include a break, crack or chip. They are reportable when diagnosed or confirmed by a doctor, including when they are specified on a GP ‘fit note’. In some cases, there may be no definitive evidence of a fracture (eg if an X-ray is not taken), but the injury will still be reportable if a doctor considers it is likely that there is a fracture. Self-diagnosed ‘suspected fractures’ are not reportable.
If it was a member of the public, it may still be notifiable
Non fatal accidents to non-workers (eg members of the public)
Accidents to members of the public or others who are not at work must be reported if they result in an injury and the person is taken directly from the scene of the accident to hospital for treatment to that injury. Examinations and diagnostic tests do not constitute ‘treatment’ in such circumstances.
All the other info, F10, newly opened etc is all stuff for your investigation to establish root cause and remedial actions to stop it re-occurring
All info in italics is taken from the HSE website:
http://www.hse.gov.uk/riddor/index.htm
Hope this helps
Will
the staff entrance was just opened after redevelopment work ie F10. Only opened for 1hr before accident 
