What's this for (except to let mice in)?

[nomorespaghetti]

We've got mice traps are set, poison is down, and we're putting mesh over all the airbricks... But I'm wondering what this is, and could it be a mouse entry point? Presumably a disused(?) clay outflow? We stuck kitchen roll up it, as you can see, to see if any water was coming out, the kitchen roll has been dry since Sunday night, but I'm really reluctant to block it in case i end up flooding my kitchen!

It's neither bathroom sink, they both drain into their respective soil pipes, and it's not the bath, kitchen sink, washing machine or dishwasher. I've never seen water drain out of it in 4 years, and it's usually covered in cobwebs.

Any advice?

It's a hole where a pipe used to come out. The pipe has subsequently been removed. A competent builder would have filled the hole with mortar from both sides, and might have added brick dust or dye on the outside to help it blend into the brickwork.

Exactly as PigletJohn said. We had mice in the loft when we moved into our current home. Blocked the couple of airbricks present (by that stage we upgraded and moved the boiler which is what The airbricks were for. When we renovated later on, the airbricks were properly blocked by our builders). We had two unused pipe holes just like that so I filled them in myself from both sides of the wall. It took me a while to match the colour on the outside but brick dust is your friend. I also filled in every small hole I could see on the outside walls as far as I could go up a ladder. Again trying to match the brick colour and the colour of the mortar - matching and smoothing out was most time consuming for me.
Unless you have a builder friend available, you can have a go yourself.
I also put poison in the loft for about a year just to make sure. The mice actually disappeared quite quickly and found some dead ones in the loft (they really are so cute, I felt bad).

Thanks both. I'm just a bit nervous about blocking it up because we're about to go away for a week, and while I'm sure it won't flood the kitchen I'll be worrying about it the whole home we're away! Tbh i think the most likely route in for the mice is through the air bricks, and we're in the process of putting mesh covers over all of those. Got about 20 traps in the house but as yet no catches. I'm going to put some poison in the loft tonight. They were getting from the loft to my son's room via the boxing of a boxed in disused pipe they got into his cot hate the little buggers!

If you don't want to block it up before you go away could you just put mesh over till you get back?

If you don't want to block it up before you go away could you just put mesh over till you get back?

It'll have to be very fine mesh to thwart mice - they have soft skeletons and can get through gaps about the width of a pencil.

www.rentokil.co.uk/mice/deterrent/

As a temporary measure, could you stuff it with those old school "knitted metal" pan scrubs?
Cheap as chips from Poundland etc.

It'll have to be very fine mesh to thwart mice - they have soft skeletons and can get through gaps about the width of a pencil.

I know that, but OP mentions putting mesh over the air bricks. I assumed they'd use the same stuff.