Looks like its going to be just post WW1.
This, said to be a 1918, looks rather similar.
This is mentioned as a Model 7, with a 1000cc JAP engine (sidevalve v-twin).
(engines made in Tottenham in London)
Great photos !
This was luxury motorcycling in its day, but do note the bicycle type brake on the front wheel !!.
It may take someone very familiar with these models to give a definitive exact year,
they were usually quite similar for years and years...
hopethishelps