We’ve heard it too! Very exciting!
If it was indeed a “twit-twoo” that OP heard, that’s likely a pair of tawny owls.
Yes Ive heard him. We live on Grierson Road. I woke up at 2am last night and it was hooting. I couldn’t go back to sleep as I was so excited
That does it - am going to go for a wonder up Blythe hill and then loop round to see if I can hear anything!
Good luck.
Success! Heard it in Blythe Hill, tracked it down and saw it perched on a tree, and it then flew off. Tracked it down again and been sat under it for around 30 minutes listening to it and trying to get a photo - I will see if I can get something better but I can only make out it’s silhouette with the naked eye, so I’ve butchered this photo and too dark to autofocus etc etc anyway this is an owl not a escaped ewok from star wars I promise!
So maybe more than one owl? One to go ‘twit’, the other ‘twoo’?
I only heard and saw the one, but quite possible there are two around.
Amazing! I’m just going out for a wander now to see if I can track the sound!
Nice! Not a bad photo at all! Looks definitely like a tawny owl to me.
Obligatory RSPB link:
For anyone who wants to go and see it (and I am no expert - this is the first time I have ever seen a wild owl) what worked for me was first off just listening - the sound is fairly regular and then finding the tree. Then trying to find it in the tree. This is the tree I took the photo of it in - can you spot it?
And this is what it looks like before I played around with the image - ie you are just looking for shapes and sometimes a bit of movement.
This is so exciting!! What time of day did you take these pictures?
I think around 9.15pm to 9.45pm . If Tawny owls as most people are suggesting, I think they are strictly nocturnal .
Be nice if there was a clear night with a nice bright moon, might have another go if that happens, but might never see it again of course - was very lucky to see it yesterday!
Cool! Might try my luck tonight then 
Hang on - is this also a cat? 
I see your cat and raise, one face of Baby Jebus 

Barking
No cats were seen in the making of this photo!
I hear an owl regularly on Lowther Hill - suspect we have a resident in Brockley Hill Park - maybe the fella we have pictured. Lovely and makes me (a country kid) feel very nostalgic!


