From an interesting post at The Cat's Meat Shop:
The average (male) Londoner of the early 1800s, out and about, was quite happy to relieve himself in the nearest alley. Urinals were becoming more common - usually outside pubs - but typically one found a quiet corner and had a pee.Note the photograph was taken this year, so the deflectors are still in place. Additional photos and discussion at the link (I always leave more at my sources to encourage you to visit them).
Those who lived in said alleys, or who owned commercial property adjoining, were not entirely forgiving of this practice, as this quote from 1809 suggests:
in London a man may sometimes walk a mile before he can meet with a suitable corner; for so unaccomodating are the owners of doorways, passages and angles, that they seem to have exhausted invention in the ridiculous barricadoes and shelves, grooves, and one fixed above another, to conduct the stream into the shows of the luckless wight who shall dare to profane the intrenchments.
Via A London Salmagundi.