Should I be worried about vermin getting through small holes in old floorboards?

[AmIimaginging]

Our existing, old floorboards have holes here and there. Should we be worried about vermin coming through? I intend to fill the bigger ones but how about the small ones? What size should I be concerned about?

I don't know why i suddenly had a panic, but I did!

I think I remember reading a mouse cab fit through something as small as a pencil hole so it doesn’t take much!

If vermin are under your floorboards them getting through the boards are the least of your worries.
I've always lived in old houses with old floorboards with holes. I've never had vermin coming through because I've been fortunate enough not to have vermin in the house
So basically if you haven't got vermin in the house they wont come through the floorboards. If you have you need to get rid

Many old houses are linked underneath. There’s no way of knowing which house in a terrace could have mice at one point and then it’s very easy for them to access other points in the terrace.

Rodents can gnaw their way through anything so small holes in the floorboards are not going to make a lot of difference. If you have mice or rats, deal with them.

There are either vermin, let's call them mice, in residence or not.

If there are mice, not having floorboard holes won't stop them. It's not about the holes it's about having the mice in the first place.

I live in an old house with holes in the floorboards. There are no vermin.

I don’t have vermin. There’s nothing to deal with. But I heard a programme on R4 about how vermin could get in and I freaked!

Similiar thing happened to me. We've never had vermin but a friend suddenly got mice and had small holes...

Yes you should. Fill them all as best you can. We had a rat in our bath who got in through a hole about an inch long. And so many bloody slugs every night 🤢