Coolant fed oil coolers are featured on later K and F engines but thankfully not on these Ds gregster! And block is uniform under the straight edge, Ady, thanks for that one. Here is the offending gasket.
Notice the burnt bridge between clyinders 2 and 3. Also those cylinder rings are ok but the number 1 and 4 cylinder rings are not withstanding the coolant and are nowhere near as clean.
Now a close up of the blown number 1 cylinder ring.(4 in Renault speak, orders are reversed...)
The ring failed and gasses at 1100 degrees celcius @ probably 400 psi made a path into the coolant jacket with ease. When parked, the pressurized coolant is forced back into the cylinder, making its way past the pistons, into the oil. Lucky people will have the water invade the cylinder at the beginning of that cylinders compression stroke and the vehicle won't start easily. When it does, only the blind will fail to notice what will appear behind the car.... Any how the water in the coolant turns into steam, rising to the top of the engine and clinging to the oil there, mixing, and creating this mess..
That mess gets bigger until it gains enough mass to fall off the rocker cover and mix with the oil, Which is one way the cooling and oil mix but thankfull in this case, at a much slower rate.
This it the cylinder head.
The exhaust valve on the water effected cylinder is a darker shade of red/brown. I can test the seal of all four chambers by simply turning it upside-down and filling each pot with petrol. The petrol will not drain if the seal is perfect. But petrol WILL find even microscopic discrepancies!
And now a useful tip to anyone suspecting foul play as this type of head gasket failure is notoriously hard to detect before the chance of heavy damage raises significantly. While servicing. (Remember, you car hasn't boiled over/ seized yet so actually checking the coolant for bubbles while running the engine may not occur.) Have a good looi at your spark plugs before throwing them away. If one of them looks like the first one here:
Then, friend, youre burning coolant
Lastly, look at the difference between pistons 1 and 4
That is a steam cleaning!
Huge pressure build-up from start-up, oil has gone a dark brown, steam galore when you remove the oil cap etc etc etc....... Im a mechanic myself and I was told at the time I could take as long as needed so it got a full head set, new bolts, new pump, belt, thermostat, auxiliary belts, cam and crank seals, reground inlet valves, rePLACED exhaust valves (Bloody bench grinder wouldn't have saved them!!) And much more. Head was also skimmed and block cleaned. It continued to burn oil after even though compression was perfect so stripped again and replaced the piston rings and by extension, big-end bearings (Job was done withoutremoving engine as was very very pressed for time.) Head was cleaned with the skimming machine as opposed toskimming as the head was perfect under a straight edge. Once again block cleaned and new gasket and bolts. Worth noting was that, rather than break, the old rings could literally be bent into pretzels! 
Rings should snap so I reckoned i might have it licked! 
It STILL burned oil 
Turned out the pcv filter disintegrated and blocked the oil drop section, sending vapour and oil to the throttle body where it was burned with the air/fuel mix. This happens in quite a few types of vehicle actually and i did suspect it but the rings, bearings, bolts and gasket were a third of the price of the rocker cover pwhich was only obtainable from a dealer... Oh well, New rocker cover and everythings been peachy. Till now.. Im going to strip it again this week, I figured I'd ask any gurus here if theres something I should look for, outside the box? I'd hate to think I messed something up the oast time.. Sorry for the mega-story, maybe itll kill some time for ye! All the gaskets I've done, all the ones ive just botched, upon request, just to get someone out of a hole, and its this one that bellies up 
Will keep that in mind for future jobs of the rover variety heh heh heh! And nice pics vauxsqueaks, So the 8v Clio IS an interference engine.... good to know 
also noticed is some "Punto style" charring between cylinders 2 and 3 even though the corresponding areas on the block and head are not burned. Thermostat opens when heated and and pump impeller is strongly attached to its shaft. Even the radiator is free and its fan working. Not impressed with the gasket just failing like that I have to say but at least it's mystery solved. 2013 eh? 
