Stranger and stranger - the DDoS protection worked, only it didn't? While I have no doubt that they received traffic from every continent (as does my home Internet connection hosting zero inbound services according to firewall logs) I'm not sure that makes it a targeted attack either. Checking their DNS history, Cloudflare has been in-place since September, so it wasn't an afterthought once things started going wrong.
https://twitter.com/rowlsmanthorpe/status/1194224258161008640
"Confirmed from a Labour source: the DDOS attack came from "a botnet with IPs on every continent."
Adds: "We use Cloudflare which soaked up the large majority of the traffic, but the DDOS-protection measures did have some knock-on effects on traffic between systems."
The counter would be hiring a botnet to DDoS a very specific part of a political opponents hours before a deadline for pamphlet printing sounds a little bit too much like " a dog ate my homework, can I have extra time?"
I'm sure we will see more evidence if it is real or it will quietly be forgotten if the cause was benign.