Tax on pension lump sum transferred from the UK to the US

I am a US citizen residing in the US. I have a Contracted In Money Purchase (COMP) private pension plan for the time that I worked in the UK between 1999 and 2010. It is my understanding that I will have to pay any tax for a lump sum transfer at source (UK). Questions 1.- Are there any HRMC process and/or forms to initiate this process? 2.- Will UK tax on this lump sum be withheld before transfer or will it be owned/paid after transfer? 3.- How can the UK tax to be paid/deducted be estimated before any transfer? 4.- Will any additional US tax be levied on this lump sum if the recipient doesn't have any income in the US? Thanks

Hi ,
 

Please refer to :  Tax on your UK income if you live abroad   . Thank you .