"They" in this context is singular, as in 'they picked up their pencil'. Make no mistake, only one person is involved here, this is not some sort of ancient traditional town stramash where they're all fighting over the one pencil.
The damage, it seems, has been done by the American Dialect Society in cahoots with the Washington Post, whose style guide has made 'their' singular since last year. These two operations claim that 'their' has effectively become accepted singular for some time now – as in "everyone wants their dog to win" (i.e. not his or her). Well not on this blog, it ain't. Here in the UK, of course, we understand it's just another example of American literary idleness – the refusal to include a 'u' in 'colour' and the use of 'z's in words like realise to name but two others. (Zzzzzz implies dozing off, of course.)
I really fail to see what's wrong with continuing with 'his or her', and I intend to continue to do so in my remaining decades on the planet. Even the LGBTQ community acknowledges that there are two genders, not one, albeit that in some cases the lines may sometimes be a little blurred. The English language is safe here.
Since I'd like to make that point clear, I've moved the recent Flash Fiction story from the front page to here.
A THEY WALKS INTO A BAR...
They cut an imposing figure in the bar-room doorway; from their mouth they blew a giant pink bubble. When it popped, everyone spun round to look.
“Goodness,” the newcomer said. “They’re playing our song.”
The pianist was playing ‘Is You Is Or Is You Ain't My Baby’.
Suddenly the newcomer became animated. “Which of you is Spartacus?” they said.
One stood up immediately. “They are Spartacus!”; then another “No – they are Spartacus!”; then another until all the bar was yelling “They are Spartacus!”
The newcomer sighed. “Doesn’t matter,” they said, drew their sub-machine gun and despatched everyone. Even the pianist.