Took a launch from Winthorpe in a K8 (AKA the non penetration meister) and scratched around for a bit. Giant cloud appeared over Newark which I knew had to be working. Headed upwind towards it, groundspeed probably 2 knots. Got lower. Then a bit lower. Got low enough that I knew I wasn't getting back. Looked at landing in the grounds of Newark Castle. Hit the sink. Got slightly nervous as I picked out the colour of people's eyes on the ground. Came out of the sink into the core some, ahem, 200' or so over the Castle and rose away like a pro to cloudbase some 5K above me.
We live and learn.