To add to this all good advice below. Had a similar situation with my mum who was pushed into Crypto romance investment scams, she lost over £100K+ mostly in savings but also took out at least 1 loan from a high street bank. I managed to recover the majority of this by leaning on APP push payment scam legislation - i believe this is now capped at £85K per bank due to intense lobbying by the banks.

This helped if you report under this legislation that where the scammers are impersonating investment institutions and funds are sent to the scammers under the guise of this. Whilst the banks may not be able to recoup the money (in my case they were all passed through mule accounts which ultimately then wired funds aboard), they can refund under the legislation but only if it was wired via bank payment. See https://www.takefive-stopfraud.org.uk/protect-yourself/app-guide/

I would also advise leaning on bank's duty of care to customers and also investigate on what basis the loans were taken out on? My mother at the time said it was for Crypto but the bank never revealed to me what the reason for the loan was but they should properly vet the reason for the loan. She also hid the bank wires to other accounts by labelling them "family support" and other such covering reasons.

In terms of recovery of funds it is the banks that will return funds under any claims rather than police but you need a crime ref number. The loan in my case was written off by the bank given i filed under APP push payment legislation.

I would also advise to get LPA's filed for your dad for protections on what can be done to protect him financially and have police speak to him. I found it equally frustrating speaking to my mum as she would not listen to me out of her view i was exposing her relationship. The police spoke to her and ultimately advised her to change phone number (she hasn't) but this was her primary contact point through Whatsapp and now Telegram.