limeyphil:
How come highways agency vehicle seem to be excempt from construction and use regs regarding rear lights?
The rear lights are in the place of the fog lamps and the fog lamps are in the place of the rear lights.
I other words the rear lights are too low for that size vehicle.
THAT would be this one then 
Statutory Instrument 1989 No. 1796
The Road Vehicles Lighting Regulations 1989 - continued
SCHEDULE 10
(Regulations 18 and 20)
PART I
REQUIREMENTS RELATING TO OBLIGATORY REAR POSITION LAMPS AND TO OPTIONAL REAR POSITION LAMPS TO THE EXTENT SPECIFIED IN PART II
- Number-
(a) Any vehicle not covered by sub-paragraph (b), (c), (d), (e), (f ), (g) or (h):
Two
(b) A bus first used before 1st April 1955:
One
(c) A solo motor bicycle:
One
(d) A pedal cycle with less than four wheels and without a sidecar:
One
(e) A trailer drawn by a pedal cycle and a trailer, the overall width of which does not exceed 800 mm, drawn by a solo motor bicycle or by a motor bicycle combination:
One
(f) An invalid carriage having a maximum speed not exceeding 4 mph:
One
(g) A vehicle drawn or propelled by hand:
One
(h) A motor vehicle having three or more wheels and a maximum speed not exceeding 25 mph and a trailer drawn by any such vehicle if, in either case, the structure of the vehicle makes it impracticable to meet all of the relevant requirements of paragraphs 2 and 3 below with two lamps:
Four
- Position-
(a) Longitudinal:
At or near the rear
(b) Lateral-
(i) Where two lamps are required to be fitted-
(A) Maximum distance from the side of the vehicle-
(1) Any vehicle not covered by sub-paragraph (2):
400 mm
(2) A motor vehicle first used before 1st April 1986 and any other vehicle manufactured before 1st October 1985:
800 mm
(B) Minimum separation distance between a pair of rear position lamps-
(1) Any vehicle not covered by sub-paragraph (2):
500 mm. If the overall width of the vehicle is less than 1400 mm, 400 mm or if less than 800 mm, 300 mm
(2) A motor vehicle first used before 1st April 1986 and any other vehicle manufactured before 1st October 1985:
No requirement
(ii) Where one lamp is required to be fitted:
On the centre-line or off side of the vehicle
(iii) Where four lamps are required to be fitted-
(A) Maximum distance from the side of the vehicle-
(1) One pair of lamps:
Such that they satisfy the relevant requirements in sub-paragraph 2(b)(i)(A)
(2) The other pair of lamps:
No requirement
(B) Minimum separation distance between rear position lamps-
(1) One pair of lamps:
Such that they satisfy the relevant requirements in sub-paragraph 2(b)(i)(B)
(2) The other pair of lamps:
No requirement
u Vertical-[/u]

u Maximum height above the ground where one or two rear position lamps are required to be fitted-[/u]
u Any vehicle not covered by sub-paragraph (B) or (C):[/u]
1500 mm or, if the structure of the vehicle makes this impracticable, 2100 mm
(B) A bus first used before 1st April 1986:
No requirement
(C) A motor vehicle first used before 1st April 1986 not being a bus, a trailer manufactured before 1st October 1985, an agricultural vehicle, a horse-drawn vehicle, an industrial tractor and engineering plant:
2100 mm
(ii) Maximum height above the ground where four rear position lamps are required to be fitted-
(A) One pair of lamps:
Such that they satisfy the relevant requirements in paragraph 2(c)(i)
(B) The other pair of lamps:
No requirement
u Minimum height above the ground-[/u]
u A vehicle not covered by sub-paragraph (B):[/u]
350 mm 
(B) A motor vehicle first used before 1st April 1986 and any other vehicle manufactured before 1st October 1985
No requirement
u Any other rear position lamp:[/u]
Visible from a reasonable distance
Seeing as that is where the Manufacturers fit the side lamps , ask them 
Land Rover Discovery I & II`s are also in the rear bumper too, unless you change to the later light cluster in the rear quarter panel to add additional side lamps , being as the wiring loom harness already has the side lamp wiring built in.