Getting a trans person's gender wrong can affect them deeply and ruin their whole day. As a trans man, I know this all too well from personal experience.
But people can avoid causing this kind of hurt by being mindful of the language they use when addressing someone who is trans.
If in doubt, instead of using 'he' or 'she', it is better to use gender neutral pronouns such as 'them' or 'they'.
Working with Fixers, I made a film to get my message across which I hope to show in old people's homes, as well as sharing on social media.
Fixers is a project of the Public Service Broadcasting Trust, funded by the National Lottery through the Big Lottery Fund, and featured on ITV.