How to save old WhatsApp photos with original timestamp?

In WhatsApp I have activated the "save to camera roll" setting to automatically save photos I receive. When it does this, the camera roll timestamp is the same as that of the photo within the WhatsApp chat.

I deleted some of these photos from my iOS 14.8.1 iPhone 7 camera roll and it's been long enough to disappear from the "recently deleted" folder.

I'd like them back in my camera roll, but when I go to the photos in WhatsApp and hit save from the sharing options, the photos in my camera roll have the timestamp from just now when I've re-saved them instead of when I received them. This breaks the chronology of the "recents" album, which is frustrating.

The only option I can see is AirDrop from within WhatsApp (hoping it gives the original timestamp) and then AirDrop back to my phone (which I know gives the same timestamp). I can try this at the weekend when I have access to a MacBook, iPad and a newer iPhone, but I'd like to know if there are other methods I should try.

Presently I have an Asus Windows 10 laptop to hand, and I could get access to an Android phone.

Thanks for any help!