The lorry was caught out on the bridge between Copper Mill Lane and Park Lane in Harefield, near the border with Hertfordshire.
Hillingdon Police posted on Twitter saying: "Road now re opened after Royal Mail driver performed the finest 900 point turn I've ever seen".
The lorry was stuck on the bridge, which has a 7.5 tonne weight limit, at around 3.36am on Wednesday (October 25).
The driver of the lorry was forced to manoeuvre his way back out of the tight, curved road, which was finally reopened more than two hours later.
Officers from both Hillingdon Police and Hertfordshire Constabulary attended the scene.
Royal Mail has been approached for comment on the incident.
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