In my wife's NHS Trust they were originally predicting the peak to come in May. Latest prediction is for the peak tom come this weekend which if it does is hopefully a good sign that the lockdown is working.
In terms of "Peak" definition I'd say they would be looking at number of daily deaths and or hospital admissions. Confirmed cases is a possible red herring as this is mainly determined by the amount of testing being done on any given day which has been variable in the extreme I believe.
Is that because the government (stupidly) originally predicted that? Let's not forget that their initial models (which they swiftly realised were utter tosh due to a lack of tests) said 10-12 weeks from the peak on March 12th.
Obviously that was never going to be the case. I genuinely can't believe the CMOs thought so. It's baffling.
Hopefully, yep, the 'peak' is this week. It's going to be a rough week. Really rough in terms of numbers you'd think and it's horrid because that's people's lives and loved ones etc.
We just have to hope we stay on course with the rest of Europe (roughly two weeks behind most of the continent) and that it is the peak (so the end of the third week of lockdown into the start of the fourth starts to see the curve flattening off).
After we're through that week, and only if we're through the flattening/start of a decline, is when I suppose we can put a target on lifting measures.
Still see us being in this mode of lockdown until at least the second week of May.
My point yesterday was with Denmark and Austria looking at gradually easing their lockdowns over the course of the next 2-3 weeks, they could give us an idea of how to do it (and conversely, a warning if they get a second spike which they can't manage).