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.

[2] In World War II, many of the company's fleet of tugs were again requisitioned, controlled by the Royal Navy examination service,[3] where they were used to patrol harbour and river entrances.

[3] Company tug Danube V took part in pipelaying activities during July 1944, as part of Operation Pluto,[3] 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.

[3] The company, by then named Tilbury Contracting Group Limited,[2] applied for admission of its shares onto the London Stock Exchange and trading commenced on 12 October 1966.

[21] This decline led to threats of legal action by former MacLellan shareholders, who had accepted shares in Interserve as part of the acquisition and saw the value of their holdings dramatically drop.

[22] The company was also forced to delay the official publication of its interim results to investors, so as "to verify the adjustment needed" as it sought to reconcile the misstatements.

[38] In October 2014, Interserve benefitted from the UK Government's privatisation of the probation sector, securing contracts to run criminal justice services in five areas.

[44] On 19 October, the firm was reported to be "battling for survival" after warning it would breach bank loan covenants;[45][46] shares slumped 38% to 55p, valuing the company at just £80m,[45] before recovering to close at 65p.

[50] On 14 December 2017, it was reported that Interserve had secured £180m in short-term funding from its banks and had pushed back the test date for compliance with loan covenants to March 2018.

[52] On 10 January 2018, Interserve warned that its debt was set to rise above £513m at the year-end due to redundancy costs and cash outflows from its legacy EfW projects.

[55] Market uncertainty following Carillion's liquidation continued, partly fuelled by a 30 January profits warning by Capita, after which Interserve's share price dropped nearly 20%.

[61] On 3 March, Emerald Investment Partners, the family firm of Punch Taverns founder Alan McIntosh, acquired £140m of Interserve debts on secondary markets in a bid to save the company.

[74] On 13 November 2018, concerns about an EfW project in Derby led to a 30% slide to a 34-year low (29p) in Interserve's share price,[76] though it later ended down just 10% on the day.

[79] The news pushed down shares 9% (closing at 33p),[80] and there was further pressure on 26 November when West Yorkshire Police said it would be seeking compensation for faults in construction of custody suites in Leeds and Wakefield.

[83][84] On 7 December 2018, Interserve was reported - for the second time in 2018 - to be in rescue refinancing talks, with banks and other debt holders (including RBS, HSBC, BNP Paribas, Emerald Asset Management and Davidson Kempner Capital) preparing to incur losses in a debt-for-equity swap that would see public shareholders virtually wiped out.

[92] Restructuring options included spinning off the £250m building materials unit RMD Kwikform to lenders, leaving the remainder of Interserve as a more focused support services business.

[95] The Cabinet Office reportedly objected to any deal involving selling RMD Kwikform, believing this would render the remainder of the business almost worthless, making it difficult to continue awarding contracts to the company.

[100] On 14 February, it was reported that blocking the deleveraging plan and removing key board members could trigger an immediate £66m repayment to lenders, weakening Interserve's financial position still further.

[107] On 27 February, Interserve announced its financial results for the year to 31 December 2018, recording a pre-tax loss of £111.5m on a turnover of £2904m (down 10.7% due to a drop in UK construction activity and tighter bidding criteria).

[126] Rival outsourcing firms including Mitie, Serco and Sodexo were reported to be considering bids to acquire Interserve's core support services business,[127] valued by lenders at around £300m.

[131] Interserve announced that Mark Whiteling, chief financial officer since September 2017, would be leaving the company;[132] and a dispute with Sandwell MBC over allegedly defective Interserve-built school buildings was reported.

[135][136] In July 2019, Interserve's partner on the Derby EfW project, Renewi, said it was resigned to having its contract terminated, with the plant's handover more than two years late.

Disposal of Interserve plc's 49% stake (valued in 2018 at £2.7m) in a Qatari business was delayed due to the COVID-19 pandemic restrictions in Qatar, so administrator EY was granted a two-year extension until March 2022.

[145] In March 2021, the construction business was renamed Tilbury Douglas;[147] Citizen Services was renationalised in June 2021,[148] and RMD Kwikform was sold four months later.

[209] A case was brought by three claimants who were scaffolders and shop stewards, against subsidiary company Interserve Industrial Services Limited (IIS) at an Employment Tribunal.

[210] IIS and the claimants trade union, UNITE, were party to a collective agreement that provided for the company to "undertake as far as is practicable to place onto an appropriate contract an NECC accredited senior steward".

However, the attackers still had access to the employee's account, which allowed them to move laterally onto other systems by exploiting vulnerabilities, exacerbated by Interserve's use of obsolete and unsupported software.

As a result of Interserve's negligence, the attackers were able to compromise 283 systems and 16 accounts, uninstall the company's antivirus solution, and deploy ransomware encrypting the personal data of both current and former employees.

Interserve disputed claims that its staff and response had been complacent, stating that it had also taken steps to reduce risks in systems supporting ongoing operations at Tilbury Douglas and in the facilities management business acquired by Mitie Group.

[217] As part of the resulting investigation, the Information Commissioner's Office discovered a number of serious breaches of data protection, which were also in breach of Interserve's own documented policies:[218] In August 2023, Interserve published its latest accounts for the 18 months to June 2021, which showed the company spent £7m on "professional adviser fees" following the attack, taking the total cost of the cyber attack to over £11M.