Here's the other half of junction 16.

The section of M25 we're now joining, from J16 down to J14, opened in September 1985, plugging a gap between existing sections around Watford and Heathrow. It's also one of the UK's busiest - you can expect a queue at this point as M40 traffic merges in, and from here to the M3 there have been successive widening schemes over the years to provide four, five and even six lanes.