This guided walking tour with Paul Talling, author of Derelict London and London's Lost Rivers (Penguin Random House Books), follows the route of the lower reaches of one of London's major subterranean rivers.

The walk starts off outside Lancaster Gate tube station, where the River Westbourne was once known as Bayswater Brook. We explore the alleyways and mews that once lined the river and the site of an ancient conduit which once supplied Central London with water. We then head off through Kensington Gardens and Hyde Park where the River formed a series of natural ponds in the park, later dammed to form the Serpentine. The River then follows the Kensington & Chelsea border with Westminster through Knightsbridge (named after a ruckus between knights on a bridge over the River) past Sloane Square where the encased river can be seen crossing the tube station and then down to the Thames where the sewer outfall empties into the Thames beside Chelsea Bridge.

The final leg of the tour takes us a few yards down the road to have a brief look at the entrance and basin of the former Grosvenor Canal and the old Chelsea Waterworks Company. This short canal was instrumental in supplying goods for the construction of Belgravia and recently the course of the canal has been made into an ornamental water feature for an expensive new residential development.

The walk ends near Chelsea Bridge, which is a 15-min walk to Victoria or Sloane Square tube stations. The duration of this tour is approx 4 to 4 1/2 hours which includes a pub break along the way.

As usual, there will be the option at the end to join Paul for a drink in a local pub to discuss dereliction, lost rivers and London trivia.

Dogs and children are welcome. By purchasing a ticket for a walk, you agree to the following terms and conditions:

* Although public liability insurance is held, the organiser shall not be held responsible for accidents, injury, loss or damage to persons or property due to participation in Paul Talling's walks. Ticket holders are responsible for their own safety while taking part in a walk. The guide is responsible for showing ticket holders sites of interest, but not to steward ticket holders across roads etc.

* The tour goes ahead regardless of the weather. No refunds due to inclement weather are given.

* The walk will depart promptly at the advertised time & will not wait for late-comers. If a ticket holder misses the walk, no refund will be given. You are strongly urged to check TFL for weekend engineering works that may affect your journey.

* Once a ticket has been purchased, the agency is unable to offer a refund or swap dates.