Southend Airport Trains
In fact the current operating times are actually even greater than set out by LtnMan -
Monday - Saturday - First train departs Southend Victoria at 0400 and is scheduled at Southend Airport Station at 0405.
Monday - Saturday - Last train departs London Liverpool Street at 0050 and is scheduled at Southend Airport Station at 0147.
Sunday equivalent times are 0615 / 0619 and 0044 / 0148 (although in reality Sunday trains are currently frequently partially replaced by a substitute bus service due to engineering.