Claiming UK tax bill on US return

I am a UK citizen resident in the UK. Having previously resided in the US I accumulated a Traditional IRA.
Last year I took a full distribution from the IRA.
This year I completed a 1040NR and managed to reclaim some of the 30% withheld by Vanguard when I took the distribution.
I am now looking to complete my UK tax return. I have been informed by HMRC the following:
- I cannot deduct US tax paid on the distribution on my UK tax return
- Any tax I have to pay HMRC on the distribution can be reclaimed from the IRS. This is due to the double taxation agreement.
Can anybody advise  on the veracity of these statements and if correct,  how I go about reclaiming the UK taxes from the IRS.
Thank you in anticipation.

It looks like you have taken a lump sum distribution from your IRA which, by tax treaty, is taxable only in the USA and not taxable at all by HMRC.  I am a USC living in the UK and in 2022 took a lump sum distribution from my IRA. It may be different for a UKC but I wouldn't think so.

In section 19 of my HMRC self assessment my tax preparer made the following statement.

"In 2022, I received a gross distribution from my IRA of $xxx. This is taxable only in the
USA and therefore exempt in the UK by virtue of the UK/USA double tax treaty so has not
been declared on this return."

Durham lad,

Thank you for your encouraging, prompt response.

I did take a lump sum distribution and I will complete my UK tax return accordingly.

Thanks again.