Not Carlton House Terrace and not Nash although similar era. Right borough but you need to go west.

Clue: Cubitt.

Not Pimlico. The other area he was famed for.
A further clue: London's reputedly most haunted pub is close by where I took this.

Getting close...
North of Eaton Sq. Quite close to another, more square, square. At the end of a mews that's not on sv. And, as I mentioned before, very close to London's reputedly most haunted pub...

Is it Wilton Mews? Corner of Wilton Mews and Wilton Street, near Belgrave Square? :-)

Wilton is right but not Mews or Street. You need to go to the other side of the Square - but almost there...

Thanks Jen. I will try Wilton Row.
It seems the most haunted pub is The Grenadier, very near... Have you checked out 'Cedric' the ghost? Geting a photo of him would make for a brilliant GWL... :-)

Sorry, Jim, benastrada just pipped you to the post (or should I say to the point).
Congratulations benastrada. You now have the distinction of guessing the first ever entry to GWL on ipernity!
I have yet to see the ghost in the Grenadier. It's quite a good pub though - very atmospheric.