The channels of the River Thames and of the estuary approaches are difficult and dangerous to navigate, especially in fog. Ships have to engage a pilot to guide them safely in and out of London. At Gravesend, river pilots take over from inward pilots. Pilots are experienced Master Mariners who have detailed knowledge of the banks, channels, lights and buoys in the river. Steam tugs were introduced on the Thames in the mid nineteenth century, to speed sailing ships on the river. In bad weather they also went out looking for damaged sailing ships, to tow them into port, earning a salvage fee.
Pilots waited aboard the cutter and were rowed out to ships in the river. The pilots Purchased Terrace Pier in 1893 and fitted it out as offices for the pilot service. A tug company also had offices there.