Agreed ER,
I think that the "best answer" in this thread is incorrect, although the DTA that I have knowledge of is the US/NZ DTA rather than the US/UK DTA. The DTA states that the country that you have residency in, has sole taxation rights to private pensions. I "think" that if I am reading the US/UK DTA correctly, it similar to the US/NZ DTA where the public pension is taxed in the country of origin (for example US social security payments gets taxed only by US despite one having residency in NZ). For the US/UK DTA, both articles 17 and 18 have applicability for you.
