84 New Barnet to St Albans. TfL only have a small interest in this, since only a small part of the route is actually in London. The service is provided commercially by London bus company Metroline. Buses are still red though! This is a famous London route and the only red bus to the old Cathedral city of St Albans with it's famous market. Mostly every 20 mins.

Timetable here
http://www.londonbusroutes.net/times/084.htm