Prosecutors are considering whether charges should be brought over the "Plebgate" investigation after receiving all outstanding evidence in the case, a Crown Prosecution Service spokesman has said.
Eight people, including five police officers, are currently on bail while the police investigation continues into Mr Mitchell's resignation
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The maintenance worker spent 10 days in hospital after plunging 9.5 metres from a scaffold tower at a disused station.
Workers and managers are to stage another strike on Saturday amid a long-running dispute over jobs, pensions and closures.
The unexpected call could prompt a diplomatic rift with China, which regards Taiwan as a breakaway province from its mainland.