Manchester so much to answer for

[pmeenan]

Are you using EV SSL Certificates? The long gaps in Chrome are the certificate verification (which Chrome only does for EV certs).

They only show up in the waterfalls for Firefox right now: http://www.webpagetest.org/result/160120...659c98237/

Requests 1,2,4,19 and 30 are all certificate checks in this waterfall: http://www.webpagetest.org/result/160120...1/details/

Depending on the performance of the OCSP responder it can cause huge gaps like you see from time to time. You won't generally see those in your local testing since the certs were recently validated and it isn't checking them every time.