The British War Office used to notify next of kin of a servicemen's death by sending them a telegram. A uniformed lad on a bike [later a red motor bike] would knock on a door and hand the telegram to a father, mother or wife.
As casualties increased people began to understand the system and dread the appearance of a telegram delivery boy and a knock on their door.
The Streets They Left Behind web site has produced a map of the homes of the 9,400 men who died
in World War I who came from the London boroughs of Highbury and
Finsbury. Each red poppy would have meant a knock on the door and a telegram.
The green poppies shows those casualties who are buried in Islington Cemetery. I suppose those are men who were badly wounded in the war and died back in London.
This page has a link to the above map and also one showing casualties from Toronto. 'By the war’s end in 1918, some neighbourhoods were devastated. Shannon
Street, a block running just south of College between Ossington and
Dovercourt, lost ten men in the First World War. The Baron family, at
113 Langford Ave. north of Pape and Danforth, lost three sons – 28, 30
and 31 years old. Robert died at Ypres in 1916; Lawson was killed by a
shell during a trench raid at Vimy Ridge in 1917; Thomas, gassed in
1915, lingered on to die in Toronto a few weeks before the end of the
There is also an interactive calendar for Toronto's WW1 deaths.