https://www.netweather.tv/forum/topic/38588-the-13th-of-june-enigma/ It’s nothing to do with the main subject of the thread (the bizarre anomaly that 13 June has never once recorded 30C, alone in all days of summer), but the point is made that in the past the maximum temperature records seemed to be spread all over the country, whereas in the past 30-40 years they have almost without exception been in the southeast corner.
A look at the Torro list of daily maxima would seem to confirm this.
As this thread has already discussed, the SE quarter of the country has warmed considerably more than the rest. In some cases by just over 2C whereas much of the rest is between 1 and 1.5C
When records are being broken then we are at the very extreme right hand side of the Bell Curve so an extra 1C warming in the SE makes a big difference to the odds of getting the record in that part of the world
I haven't done the maths but it is about the probability of getting a value N sigmas (standard deviations) away from the mean