Bearing mind that I'm woking from the linked version of the TSRGD "As enacted" ie, it may have been amended, that looks like something under Schedule 13 Part 9 "Other temporary signs"
I'll not suggest a quiz asking what's non-compliant about that (yellow) sign but I think the background should be red and the lerring whit as prescribed in Part 8
8.—(1) This paragraph applies if the sign—
(a)conveys a temporary hazard warning;
(b)conveys only temporary information for pedestrians, cyclists or pedestrians; or
(c)indicates the entrance to, or exit from, road works for vehicles involved in the carrying out of those works.
(2) The background must be red and any letters, numerals, other characters, chevrons or borders must be white.
(3) This paragraph is subject to paragraphs 10 and 11.
I saw this unusual roadsign near Goudhurst, in Kent, a few years ago. It's a sign for a local house just off the road. I was interested and looked up the meaning of the words on the sign- it's Manx Gaelic for 'country seat'. Mystery solved!
The English wording was sent by email to be translated. The reply was duly printed on the sign. Unfortunately, it was an auto-reply in Welsh for "I am not in the office at the moment. Send any work to be translated".
Quite right too! That horizon needs to be levelled before they let any boats sail over there. They might slide off the side of the world, like a conspiracy theory fan on twatter or a Tory economist proposing the impossible.
Cugel, only a dry land navigator.
“Practical men who believe themselves to be quite exempt from any intellectual influence are usually the slaves of some defunct economist”.
John Maynard Keynes