Is this the legal or not?

I think that tyre’s legal myself.

It’s clear that those slits are intended to wear out before the main grooves, I could be wrong but I think those slits between the grooves are to help with noise reduction, but don’t hold me to that :wink:

Section 27 - The Road Vehicles (Construction and Use) Regulations 1986

“tread pattern” means the combination of plain surfaces and grooves extending across the breadth of the tread and
round the entire outer circumference of the tyre but excludes any—
(i) tie bars or tread wear indicators;

(ii) features which are designed to wear out substantially before the rest of the pattern under normal conditions
of use; and

(iii) other minor features; and
“tread wear indicator” means any bar, not being a tie-bar, projecting from the base of a groove of the tread pattern of
a tyre and moulded between two or more features of the tread pattern of a tyre for the purpose of indicating the extent
of the wear of such tread pattern.