UK capital gain tax on RSU's granted in USA

Early this year I sold some restricted company stock I granted 4 years ago from my former employer and moved the money from US to UK. The US brokerage account has already withheld a portion of the shares to cover federal tax withholding. This year I am no longer resident of US and am a resident of UK. My questions are: 1. For these money, I only need to pay for the Capital gain tax in UK since they are already taxed in US(aka US income tax)? 2. Is there a guideline to file the tax return for RSUs granted from US?

Hi,

Tax was payable at the time the stock was vested and US tax was witheld then.  

As you are now disposing of the stock, only Capital Gains Tax is payable on any gain arising from the disposal. The receipt of any foreign income and, or, capital gains is criteria for completing a Self Assessment tax return.

Thank you.