Refused, then granted B1/B2, now need to apply for VWP

I had originally been refused a US visa back 2001 in India. Shortly after this I was transfered by my employer to work in the UK, later, under different circumstances applied for a visit visa in 2008 at London and was granted a10 year B1/B2 visa on my Indian passport (with 5 year UK WP).

I travelled to the US several times on my B1/B2 visa for personal & business trips.

I am now a British citizen with a British passport and need to travel on Business to the US, how can I mention all this on the ESTA website? All it asks for is if visa was. Ever refused and where

Submitted ESTA as per situation and got approved