Nearly seven pillar boxes then appeared in London (8,5-4)

I believe the answer is:

eighteen fifty-five

This clue is a double definition.

'nearly seven' is the first definition.
(18:55 is nearly seven o'clock)

'pillar boxes then appeared in london' is the second definition.
(London post boxes were launched in 1855)

I've seen this clue in The Guardian.

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