No dont take a pic except for you!
Get the cat chipped asap and vet checked, vaccinated..........Flu only, an older cat will not need luekemia.
The cat may not want to go out so dont force it!
Depending on age the cat may still leave the garden!
Try to start with same food as its currently on.
2 litter trays to start with and use same litter also if possible.
I lived in London and only knew the cats LOL................think everyone knew my cat flap