HM Customs and Excise Double Taxation Treaty Relief form

I got pointed at this form https://assets.publishing.service.gov.uk/media/637e192f8fa8f56eabf75e5b/Double_Taxation_Treaty_Relief_Form_DT-Individual.pdf for asking to get my UK pension lump sum taxed in Japan rather than the UK. I’m fully tax resident in Japan, and will cash out rather than take an annuity.

Has anyone tried this form before? Do you need a translation to get the Japanese stamp or other preparations?

by KenYN