Picture the scene, it's the middle of the night in deepest, darkest Lancashire. Two total tear-arses are having this very same argument about whether it's possible to get an ESP equipped car to go stupidly sideways. To make things easier we'll call the ESP believer "Eddie", and the old style physics devotee "Pete"[1]. The car involved will be a Focus 2.0 Zetec ESP 3 door, a purple one, W reg and less than 3000 miles old.
The purple Focus is travelling along Atherleigh Way, which is a large, straight road which leads from Leigh to the East Lancashire Road. "Eddie", who's the passenger is goading "Pete" into attempting to take the turn onto the East Lancs. Rd at 80+ mph "because it's an ESP one, it'll do it no problem". This is what triggers the experiment...
"Pete" decides to prove "Eddie" wrong.
The Focus is approaching the East Lancs at 95 mph, "Pete" has remembered that the East Lancs is particularly worn at this junction, and that the crown of the road is a bit more sudden than is the norm. "Pete" steps on the gas that bit more, and as he approaches the lights for the junction does the old "Flash the headlights at the traffic lights" trick. The lights change to green as the purple Focus approaches. "Pete" gives it more gas.. "Eddie" is beginning to look worried. "Pete" has a stoopid grin, and is wondering to himself if he's going to manage to pull this off without dying.
The Focus suspension starts to compress as it crosses the crest of the East Lancs, just as this is happening "Pete" starts to turn right.. the Focus begins to turn in.. "Pete" stays on the gas and the Focus begins to understeer slightly.. it's doing well considering the thrashing it's getting.. The front wheels begin to go light as the front of the car crosses the crest of the first carriageway, "Pete" backs off the steering a touch to try to keep the car neutral, but has this suspicion that he's probably, finally, pushed the Focus beyond its capabilities.. The rear of the Focus comes off the crest and goes very light.. the Focus begins to oversteer in a huuuuuuge fashion.. "Pete" has still got his foot on the gas, the front of the Focus is *facing* the Armco barrier, and "Pete" is holding the car on full opposite lock, at full throttle, at probably still 85-90 mph. The ESP light on the dash is just *on* there are all sorts of pumps and things going nuts... The ESP is trying to slow down the car, when it needs to go faster.. "Pete" presses the ESP button "off" and the Focus straightens up and continues down the East Lancs in a happy fashion.
"Eddie" never goaded "Pete" about whether it was possible to get an ESP car sideways again..
"Pete", on the other hand, thanked the Ford for it's ESP making the corner possible, while cursing it for trying to kill him when he needed to power out of it.
I'm pretty sure that Focus could have rolled at any moment if "Pete" hadn't known what to do. It was the closest "Pete" had come to rolling a car and the last time he's going to take that corner at such a bloody silly speed in a hire car again.
[1] The names have probably been changed to protect the guilty.