In reply to a post by DrTeeth:

Radiation pattern of router antenna(s), metal in path of signal when transmitter is in office, location of receivers, orientation of receiver antennas and their receiving pattern etc

He tried several different wireless access points in the office, and various items, such as laptops, tablet, phones around the house. They all performed badly when the wireless was located in the office, even visiting friends complained the wireless seemed slow.

The office is a small bedroom, in the centre rear of the house, so no unusual location.

Perhaps somebody at some stage of the Cold War made that room nuclear radiation proof [cough].