EU referendum: Can you bring your own pen to the polling booth?

Social media users are warning EU referendum voters to bring their own pens to polling booths on Thursday over fears that
pencil marks on ballots could be compromised.While pencils are traditionally provided by electoral staff inside each booth,
it is not a legal obligation to use them.Ballots with an 'X' marked in
pen or pencil will be accepted and counted.
The Electoral Commission told ITV News that voters are welcome to bring a pen and that counts are observed by statutory observers to ensure neutrality.
Campaigners from both sides are also invited to counts to observe proceedings.
By tradition, pencils are available in polling booths for voters to mark their ballot papers. If a voter wishes to bring their own pen and use that, it's fine.
In regards to security, at the count there are statutory observers to make sure that they are carried out correctly. Campaigners are also invited to observe the counts taking place.