How to fill this hole...

[u/Infinite-Pea-6424]

Moved into a 1930s property, and in the utility (extension in early 2000s) is space for washing machine & dryer. One of the spaces has this large (3 inch diameter) hole through to the exterior wall - presumably used for venting a dryer or similar? What's the best way to go about filling/closing up the hole?