Here’s a pic of the ECS on its way to Southend before the high speed run later in the day. It had to run under special conditions when it exceeded the speed limit, which included double blocking and of course the 75mph on the OLE wasn’t an issue.There are 60(?) mph speed restrictions through Laindon & Pitsea, both due to curvature, but ISTR that an HST was allowed to reach 100 mph near Hornchurch many years ago. (LT&S 125th anniversary ?) Pitsea to Benfleet is straight, but possibly the somewhat soggy ground conditions might cause a problem for 100 mph running.