Some retailers refuse to throw away edible food. They give it to the poor.
Pret is a very tasty but slightly expensive sandwich shop that sells authentic coffee. It is the luxury option that most people can enjoy.
Pret is now partly owned by McDonald's but this should not put you off. The policies remain the same but maybe the new managers shout about them more.
In addition to this by buying a meal there you will generally contribute ten or twenty pence to their charity fund. This is not a great deal of money but I believe it is spent well.
I would guess that 90% of these meals will go to men. This is important as men are often overlooked by the authorities.
The first photograph is of Leadenhall Market in the City (which has a Pret). The second is some street art from trendy Camden.