Thai Square Hanover Square

Do a good business express lunch, 2 courses for £x, decent food, quick turnaround and a good place for entertaining over lunch.

Part of a chain, this particular restaurant on Princess Street is a gem.
It is tucked away off of Regent Street, so when a hard days shopping has gotten to you, this place, rather than the obvious tourist-filled fuel stops on Regents / Oxford Streets is a great place to rest your weary feet under a table.
The menu is huge (as in lots of choice, not as in conversation blocking, Berlin Wall-esque weighty tome).
The food is very well priced and just brilliant. Unlike some Thai restaurant chains, they don't rely heavily on the Western-friendly dishes; walk away from the green/red/yellow curry and I promise you won't be disappointed.
The staff are A-typically discreet but very freindly and good for a reccomendation or two. A decent wine list and erring on the right side of dark yet comfortably lit, I cannot recommend this place highly enough.