Concrete rectangles at the ends of runways.

For ages I have wondered what these concrete rectangles found at the end of some RAF runways were for.
The pictures are of Duxford and Swinderby but plenty of others have them.
Any ideas?

Thanks.

guessing lighting, but I am no expert

Similar set up at Wittering

I did wonder if that is what they were for but the differing distances from the runway thresholds found at various airfields made me think they may have been for something else.

I suspect that term has been rattling around in the jargon of the MOD for a number of years!

Edit, I should have added secretly.

My guess is footings for VASI's. Variable Angle Slope Indicator. Low rectangular boxes containing coloured lights visible to a landing pilot. Green if on the glideslope, red, if too low. That kind of thing. More on how it works on google, but few images of the lights.

The similar ones on 36/18 at Abingdon were for the arrestor barrier.

Cranwell has the same (or similar) arrestor set up and the pads seem larger

I thought about arrestor barriers but discounted the idea because of the distance some of them are from the threshold. Also, I don't know of dates, but many of the airfields that have these rectangles in place were closed before barriers were introduced?
Also if you look at the attached GE grab of Linton on Ouse this has what looks like a barrier at the end of the tarmac and rectangles on the grass 150ft further back from the threshold, it is the same at the other end.
None seen on the other runway.

Using GE:
(And no, I don’t have anything better to do today!)

Duxfords surviving ones are spaced about 35ft from the end as are those at Horsham St Faith although apparently only on one runway.
None visible at North Weald, North Luffenham, Wymeswold Ouston or Biggin Hill, or what is left on GE of Tangmere,
West Malling has them close to the threshold and Oakington about 50ft back, with Waterbeach about the same distance.
It looks like Leconfield may have had them at the northern threshold and Middleton St George at both ends and Leuchars at 08.
Valley and Mona have them as does Shawbury and L Rissington on the main runway. Kemble at the 09 end and even Barkston Heath has them on two runways.
Benson on rwy 19 and evidence of them at Pershore on the northern threshold.
Possibly at Honington.
Each end of the runway at West Rayneham.
As mentioned both ends at Wittering (but not Cottesmore or scampton etc ) and also on main runway at Syerston.
Possibly 02 at Finningley.
Each Runway at Brawdy.
Possibly one at Church Fenton rwy 24.

There must be a common denominator in there somewhere with the many bases that don't have them.
With no scientific approach other than just looking at dates possibly all of those with the rectangles were operational after 1960.
So lighting/VASI for certain aircraft types likely, and Peter Kirks SNUP the most likely !

Ok, I think I have answered my own question and hands up all those who said arrestor gear..
Checking back through a June 1975 RAF En Route Supplement for something entirely different I noticed that West Rayneham had 'Safe Bar 6 ' 30 ft from the threshold, GE shows the rectangles at about that distance.
Ditto Linton on Ouse RAF Mk5 but at 200 ft overun .
Wattisham Safe Bar 6 at threshold.
Little Rissington Mk5
And so on...

Next question of course is when these systems were introduced, what aircraft types were expected to engage them and why, as in the case of Linton were they located so far from the end of the runway and on grass?
If West Rayneham had Safe Bar 6 then I assume that the system was capable of handling the likes of Hunters and Javelins?