As road spotters will know, the A10 has been detrunked (downgraded from trunk to primary). The bit from London to Cambridge was done in the 1990s, and the bit from Cambridge to King's Lynn in 2001. OSM still shows it as a trunk road, so I'm retagging it all. On the way, I've noticed a few more roads with delusions of grandeur, so I might come back to fix them later.

I'll head off some possible objections:

"But the road signs on the A10 are green." - Yes, I know. A green road sign means primary, not trunk. There is no special colour for trunk road signs. The colour system used by OSM is different: green for trunk and red for primary. I don't like this, but that's the way it is.

"But it looks wrong with all the green roads changed to red." - Sorry, but that's the map renderer's problem. The underlying data, i.e. the tags, must be made correct, regardless of what the renderer does with them. There aren't that many trunk roads, so the map is going to get a lot redder when people fix all the tags.

Correction: the entire A10 was detrunked in 2001. (Earlier, I mistook the realignment of a minor bypass in 1993 for the wholesale detrunking that happened later.) The relevant statutory orders were "The A10 London-Cambridge-King's Lynn Trunk Road (A47 King's Lynn to A14 Milton, Cambridgeshire) Detrunking Order 2001" and "The A10 London-Cambridge-King's Lynn Trunk Road (M11 Junction 11 to A505 Royston Hertfordshire) Detrunking Order 2001".