File:Hanwell Asylum.jpg
It was from a post card's (Chester Vaughan series) with a postmark stamped 9 pm May 16th 1904. These post cards were very popular in England around this time. If posted locally in the morning they would arrive the same day. From the hackneyed phrases and banal messages written on the other side they seem to have been the e-mail of their day.
Source: I scanned it from post card, then cropped and enhanced image.