It was 15:30 on a Wednesday, and a man was threatening to throw himself off a bridge and into the path of an oncoming train.
As emergency services tried to talk him to safety, which they did, Allison Dunn was left with a different problem - the rush hour.
As South West Trains social media head, she knew thousands of commuters were about to descend on Waterloo - London's busiest terminal - and many would turn to their phones for information.
At 15:33, she tweeted on the official
South West Trains Twitter account: "All lines through Wimbledon station currently blocked owing to emergency services dealing with an incident at Wimbledon. More to follow."
