Task: Question Answering
Input (English): Passage: The town of Herne Bay took its name from the neighbouring village of Herne, two kilometres inland from the bay. The word herne, meaning a place on a corner of land, evolved from the Old English hyrne, meaning corner. The village was first recorded in around 1100 as Hyrnan. The corner may relate to the sharp turn in the minor Roman road between Canterbury and Reculver at Herne.One of the oldest buildings in Herne Bay is the late 18th-century inn The Ship, which served as the focal point for the small shipping and farming community that first inhabited the town. During this time, passenger and cargo boats regularly ran between Herne Bay and London and boats carrying coal ran from Newcastle. From Herne, there was easy access by road to the city of Canterbury and to Dover, where further passage by boat could then be obtained across the English Channel to France.
The 1801 census recorded Herne Bay, including Herne, as having a population of 1,232. During the early 19th century, a smugglers' gang operated from the town. The gang were regularly involved in a series of fights with the preventive services until finally being overpowered in the 1820s. In the 1830s, a group of London investors, who recognised Herne Bay's potential as a seaside resort, built a wooden pier and a promenade on the town's seafront. This and the subsequent building of a railway station led to the rapid expansion of the town; between 1831 and 1841 the town's population grew from 1,876 to 3,041. The London businessmen intended to rename the town St Augustine's, but the name was unpopular with residents and the name "Herne Bay" remained. In 1833, an Act of Parliament established Herne Bay and Herne as separate towns. Local landowner Sir Henry Oxenden donated a piece of ground for the site of the town's first church, Christ Church, which was opened in 1834. In 1837, Mrs Ann Thwaytes, a wealthy lady from London, donated around £4,000 to build a 75 feet (23 m) clock tower on the town's seafront. It is believed to be the first freestanding, purpose-built clock tower in the world.During the 1840s, steamboats began running between Herne Bay and London. There was a type of beach boat unique to Herne Bay and nearby Thanet, known as the Thanet wherry, a narrow pulling boat about 18 feet (5 m) long. These boats were mainly used for fishing; however, with the advent of tourism and the decline of fishing, they became mainly used for pleasure trips. A document dated 1840 records the town as having the following schools, all of which are now defunct: Haddington boarding school, Oxenden House, The British School, Prospect Place and Herne Street School. The village of Herne was often called Herne Street around this time. The same document also mentions the still-existing Rodney Head, The Ship and Upper Red Lion inns. 
Question: What three things did the London investors build that led to the rapid expansion of the town?
Output (English): a promenade.