Sadly not nineteen (yet), but tonight's SEO tally at PC Wandering's patch escalated to nine.
I squeezed an hour in from about 6pm and there were four quartering the two fields near the rusty five-bar gate as the light faded.
And then there was a wee melee above the main field as vulture-like (in the cowboy films), five rose on the thermals and were joined by a sixth and a seventh and the whole group lifted ever skyward.
Another two were located at ground level and the maths is now easy.
I have never seen more than two SEOs at once, as far as I can recall, and I have never seen this breathtaking behaviour where whirlwind-like, a few birds 'suck in' others and they all amicably gather.