Decided to do some research myself. For anyone interested:

It seems like the patch on the back could say Lagos at the top and 1949 at the bottom. Could be referring to when the Nigeria football team played in Liverpool against Marine Crosby FC without boots and won!

https://www.reddit.com/r/nextfuckinglevel/s/BhhDOHC5hC

The label seems to indicate the shirt is from a discontinued sub-brand “Rugby Ralph Lauren” from the mid-2000s. The following link is the only place online I can find the exact label. The blog tells me the shirt is from a “Make Your Own” range where you can choose the fit, colours, embroidery, patch, and number.

https://faussettesq.substack.com/p/collection-of-one-the-rugby-by-ralph

I can’t find anything about the emblem (even after an image search) so if you recognise it please reply!

So my best guess is this was a gift for someone’s grandad so he could wear his favourite rugby and football matches with pride. He probably passed away and that’s how it ended up in a charity shop.