Removing the rear fog lamp from your mk1 and wiring up the upper break light to work as it? (so it comes on when you brake, but stays on when the fog lamp is activated)?
Could the lamp be modded to accept two bulbs even? Maybe LED bright ones.
It would pass an MOT I’d have thought, and also be a nice little mod in smoothing the rear end of your Mk1!
Ideas/Opinions?
Thanks
Phil.
On second thought, would it be too high? as a fog lamp is usually situated low on the car.
Has anyone substituted in a different casing to make the original look nicer?
It is acceptable to use the centre brake lamp as a fog lamp but using it as a duel purpose lamp may cause problems at MOT test time. The testers manual says that a fog lamp must not “be adversely affected by the operation of any other lamp”. I think it would come down to the tester. I think people have put an “MOT switch” in the boot that switches the centre brake lamp over to a fog lamp for MOT, then you can switch it back again after.
My 1991 J Ltd Roadster has the boot brake light working as the rear fog and has always been fine on MOT. Not sure about the dual purpose idea. When the fog light laws came in a few years ago when I was in the trade they had to be mounted 4 inches from the brake light, but that may have changed over the years.
The regs are here
My middle brake light is also my fog light - thanks to a couple of diodes in the wiring. The bulb has feeds from both brake and fog light circuits but both feeds have diodes in them so the fog light circuit doesn’t light up my brake lights.
3 MOTs passed with no problems. Not that my success means it’s right, I may just be lucky.
Unless you fit a new bumper to your UK Mk1, it won’t smooth the rear, since you’ll be left with a big hole.
Not always true in Roadsters; depends how the foglight was fitted. By far the worst setup are foglight bolted through the numberplate finisher.
Well I’ll fill that.
Two pieces of plastic, one the size of the hole, and one larger mounted behind, spray it up and stick it all on. All I SHOULD be left with is a small gap/body line, like it is a removable section of the bumper…
Thanks for the replies! Looks like it’s a goer! Will do it! 
I’m guessing the diodes are used to direct the flow of to the brake lamp FROM the rear brake lamps, and to stop the flow from the rear fog going to the brake lamps?
Thanks
Phil.
I did it a differnt way, keeping the high level brakelight, but used one of the reversing lights as a fog light with a chrome bulb. Took the low level fog light off so all looks nice and tidy, and you still have that extra brake light to warn the idiots behind you. Changed that to LED and its really bright.
Yep, the diodes are used to direct the flow of to the brake lamp from the rear brake lamps, and to stop the flow from the rear fog going to the brake lamps. This lets you keep the high level brake light and gives you an unobtrusive fog light too.
The reverse light mod is just as neat and doesn’t need diodes.
Lots of options:-
If you have a UK spec car and you remove the fog light you are left with a hole in the bumper. I fitted a smaller lamp (about 12cm by 5cm) It cost £2 at an autojumble and is one of the type that were fitted as aftermarket items to 60s cars. I had to do a lot of work with a powerfile to get the hole higher and to the right shape. I’lll try and post a picture.
If you have a Eunos you could cut a hole in the bumper and fit the boot brake light from a scrap MX5 or a lamp like the one I have.
You can fit a red bulb in the right hand reversing light (LED or conventional). Cut the feed from the reversing circuit and supply the feed from the fog light. Technically this contravenes the “Construction and Use” regs (because the light does not have a symbol on it to indicate that it is a fog light!) but MoT testers don’t know or care about that.
You can use the boot brake light as a foglight, but you will need to fit one or two diodes so that the other brake lights do not light up with the fog light.
Pete
I really must learn to type a lot faster…
Pete
Awesome replies people! Would be interested to see that pic! I considdered a peugeot 206 upper brake light, fitting it upside down in place of the original fog but that would be a fair bit of work and I prefer the ‘smooth’ look anyway. Still like to see a pic of yours tho.
I’m going to go for the upper rear brake I think, as it does not require fitting another bulb and therefore is less hassle… I’m also OCD and like the idea of the fog lamp being in the middle! LOL Must look a bit like an F1 poor weather lamp when its on! 
I’ll do a write up/how to when I do this.
Thanks again
Phil.
Our previous import had the right hand reversing light tinted red! It always passed the MOT even though one guy retinted it as he said it was getting ‘pale’ Back end looks so much nicer without the dangling appendage[:)]
Wouldn’t a brighter fog light bulb risk overheating the plastic 3rd brake light housing? It’s just a thought 
