A Community Network for Bowes Park and Bounds Green
There are posters locally for a recently lost stripy tabby that roughly resembles this cat. Don't have any more details than that on hand, but there are posters on the railway footbridge at Bowes Park.
This looks very much like our cat, Dennis, who tends to roam a bit further afield than we'd like, and who apparently disappeared for long periods when we were on holiday from August 21st to 25th. Anyway, Dennis is back now, so if the cat in the picture is still living on your windowsill then it's not ours.