Sahar lives in Sutton, Surrey. She has to attend a meeting in Coventry at 10am. It will take her an hour and 20 minutes from her home to get to Euston Rail Station, from where she will get a train to Coventry. The train journey from Euston to Coventry is an hour. Trains to Coventry run at the following times: 15 minutes past the hour, 30 minutes past the hour and 50 minutes past the hour. The meeting venue in Coventry is a 5-minute walk from the station. What is the latest time that Sahar can leave home, if she is to make it on time for the meeting in Coventry? Show your working.