The BBC reporter who sent a tweet mistakenly claiming Queen Elizabeth had died had not been told the station was running a rehearsal of how it might cover a royal death.
A report from the BBC Trust's Editorial Standard's Committee said "some news staff" had been emailed about the plan and told not to discuss it, but added: "A journalist working for the BBC's language services, who had not been sent the email, saw an internal TV monitor which was showing the rehearsal.
"A number of tweets were sent from her account. The first stated that the Queen was being treated in hospital, the second stated that the Queen had died."