Originally Posted by MH017

Were you parked next to the Terminal or opposite the runway at the 'new' apron ? In that case you even have to take a bus'trip' (busses can only go 40kph according to the traffic signs), so, this alone will take you 15-20 mins, if flight is on time...so, with a 45mins transfer, this will only give you 20 mins to clear the horrendous security check and proceed to your new gate...

I always take at least 1hr30mins minimum transit-time @ DOH to create some buffer; suggest you take an earlier LHR-DOH flight for your DOH-TYO connection (and check also your TYO-DOH-LHR transit time)...