I need to get flight connections from 'Terminal 1 going to terminal 5' and I cannot really afford to 'screw up'. I am fairly world travelled and understand walking should take about 10 minutes. (Probably my best option). There would possibly be a Wait on terminal buses and train (Underground). Please clarify if there is an 'internal airport train' that Continually goes around each terminal ? Also please clarify the actual number of train services going from terminal 1 to 5 ? I read heathrow Express, Heathrow Connect..., I appreciate some help as bit unclear.