Comment by ZoneZealot

I agree, and I also am familiar with how WP Engine's 'GES' (global edge security) works. obr.uk points to two IP addresses held in the name of WP Engine, but they're actually BYOIP with Cloudflare. Cloudflare act as a caching layer, DDOS mitigation and WAF.

Note that GES works a bit different to traditional Cloudflare implementations, HTML requests are basically passed through to the WP Engine NGINX reverse proxy server that's in front of the WordPress site (as opposed to being heavily cached with Cloudflare). Static assets, like a PDF - would indeed be cached with GES.