Living in EU, Double taxation - claiming back tax

I live in Portugal and am paying tax on my private pension both in UK and Portugal. I left UK on 1st April 2021 and have been a tax resident in Portugal since. Could someone advice me please how I can claim back the tax I paid in UK since 2021 as I'm also paying tax on this in Portugal. I understand Portugal has first right to UK private pension. My questions are: (1) how I can claim this tax back and (2) how I can stop HMRC claiming this tax in the future. Many thanks for any help.

Hi ,
 

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

Thank you .