As a result of an Act of Parliament, the company running the Brent Reservoir acquired more land. An increase in traffic on the Regent’s Canal had meant that more water was required to replace the loss from its locks.

The land was used to increase the height of the dam and the reservoir’s area expanded to 400 acres by 1854. The reservoir works included raising a new embankment to protect from flooding a tavern called the Old Welsh Harp which was situated just north of the Brent Bridge.

The pub may have been already existed as the ’Harp and Horn’ by 1751 but had become the Welsh Harp by 1803. It was also known as the Lower Welsh Harp.

In 1858 the lease of the Old Welsh Harp was taken over by William Warner of Blackbird Farm in Kingsbury. He created a large pleasure gardens behind the pub and obtained the rights to use the reservoir for recreational purposes. For the following 30 years the ’Welsh Harp’ became a very popular leisure destination.

Warner organised fishing and boat hire, ran competitions for swimming. Sports flourished including horse racing, bowls and cricket. Warner built a music hall and restaurant beside the inn.

A station called ’Welsh Harp’ was opened on the Midland Railway in 1870 at Warner’s request. Special trains on bank holidays brought thousands of people from London to fairs in the Welsh Harp’s grounds. Part of Warner’s legacy is the name by which the reservoir is now known.

At the end of the century, Warner died. The popularity of the tavern and its pleasure gardens declined and Welsh Harp station closed in 1903.

The pub was demolished in around 1970 to make way for the southerly extension of the M1 motorway.