Interserve was a British construction and support services business based in Reading, Berkshire, which went into administration in 2019 and was formally wound up in 2022. In 2019 the group generated revenue of £2.2 billion and had a workforce of 34,721 people.

The company was founded in 1884 as the London and Tilbury Lighterage Company Limited. From 1991, it was known as Tilbury Douglas following a merger with RM Douglas, but in 2001 it rebranded as Interserve plc. The name change partly reflected a shift in focus during the 1990s towards maintenance and facilities management services sectors, and this continued in the 2000s, buoyed by further acquisitions.

However, financial issues including problem contracts in Interserve's energy-from-waste business led to profit warnings in 2017. The company was forced to restructure and refinance in March 2018. After its financial situation worsened in late 2018, debt holders discussed further financial restructuring of the business. A debt-for-equity plan was rejected in March 2019, and Interserve plc went into administration owing creditors over £100m. In a pre-pack deal, the rest of the group was immediately sold to a newly incorporated company owned by lenders, Interserve Group Ltd, and a break-up of the company followed. Interserve's facilities management business was sold to Mitie in December 2020, and RMD Kwikform was sold in October 2021 to France's Altrad.

In March 2021, Interserve resurrected the Tilbury Douglas brand for its construction and engineering services businesses. Interserve plc was formally wound-up in the High Court in January 2022. In June 2022, Tilbury Douglas fully separated from Interserve Group and became a standalone construction contracting company. Some smaller assets are expected to be sold before Interserve Group is finally shut down in 2024. In October 2022, Interserve was fined £4.4 million for a breach of data protection law in May 2020.

Interserve could trace its origins to 1884, when the London and Tilbury Lighterage Company Limited was formed to transfer goods by sailing barge to and from ships on the River Thames, London, England. In 1888 the company expanded into dredging, securing a contract with the Port of London (PLA) to remove dredged ballast. The company changed its name several times, eventually operating for 56 years as Tilbury Contracting and Dredging Company Limited (TCDC) from 1908. Several of the company's vessels were requisitioned for war duties during World War I where they took part in various military campaigns including in the Dardanelles, Archangel and the Persian Gulf. Lightering gradually declined due to the increase of road traffic, and dredging became the mainstay of the company. In 1938 the company's lighterage fleet was amalgamated with vessels owned by W H J Alexander Limited and Tate and Lyle Limited to form Silvertown Services Limited and TCDC severed its links with its original business activity.

In World War II, many of the company's fleet of tugs were again requisitioned, controlled by the Royal Navy examination service, where they were used to patrol harbour and river entrances. TCDC tugs and barges were also represented within the merchant marine fleet that took part in Operation Dynamo, commonly known as the Dunkirk evacuation. In June 1944, company tug Danube VI participated in Operation Neptune, the D-Day invasion of Normandy, known as the Normandy landings by towing the 'Phoenix' (mulberry harbour breakwater units) and 'Whale' (floating roadway units that connected the mulberry harbour pier heads to the landing beaches), as well as ammunition barges from Littlehampton across the English Channel to the Normandy beachhead. Company tug Danube V took part in pipelaying activities during July 1944, as part of Operation Pluto, which brought together British scientists, oil companies and the armed forces in the construction of undersea oil pipelines under the English Channel between England and France to transport fuel supplies to Allied forces on the European continent.

As the UK sought to rebuild infrastructure after World War II, the company established a civil engineering capability in the 1940s to participate in this activity; together with building these had become the company's focus by the 1960s. In 1964, a Port of London Authority dredging contract ended, 76 years after it was first awarded, and the company ceased to operate as a dredging contractor in the UK. In 1965 the remaining fleet of dredging vessels was sold to Westminster Dredging Company Limited. The company, by then named Tilbury Contracting Group Limited, applied for admission of its shares onto the London Stock Exchange and trading commenced on 12 October 1966.

In 1991 Tilbury acquired RM Douglas, another construction and civil engineering business, the combined business becoming known as Tilbury Douglas. Although both groups had a UK-wide presence, the rationale of the acquisition was that the two companies complemented each other. Tilbury Group was headquartered in Reading and predominantly involved in building work in the South of England and in Scotland, while R M Douglas was headquartered in Birmingham and its strongest regional presence was in the Midlands and the North of England with a strong bias towards civil engineering projects. In common with many major national and regional contractors in the post-war period, R M Douglas successfully bid for work in the construction of airfields and motorways where it completed various UK motorway building projects in the 1960s, 1970s and 1980s.