Yes is on a single ticket. Booking is done directly with cathay pacific online and reconfirmed timing via phone call. I did challenge the telephone advisor about the 85 mins transit but was told not an issue as in same terminal.
Only until I landed, i realised is a very long walk - from one end to another. If only the gate ground staff helped me to inform my next plane, I would have caught it as my boarding pass already issued at LHR.