How to proof my Split Year date start ?

My situation is that i entered into UK by BNO visa on 1 July 2021 (Passport No 12345) , but in Nov. 21 the entrance passport has been renewed to a new passport (no 34567) . In later months an UTR applied with the passport no 34567 , but the UK ViSA & immigration office only got the record of my entry to UK on 1July 2021 was (Passport No. 12345) . So if in any dispute regarding the split year date how can I proof myself by using passport 34567 to check with the UK Visa & immigration as it (34567) wasn't exist in July 2021 .

Hi
If you have your old passport, it will still show your date of entry in that.
Thankyou.
Regards.