[2] During World War II and after the Fall of Singapore, Changi Prison became notorious for its role as a prisoner-of-war camp for Allied soldiers captured by the Japanese.

[3] Many of these prisoners were subjected to brutal treatment and forced labour, and a significant number died from malnutrition, disease, and mistreatment.

[10] Deliberations in the Legislative Council saw opposition to the subsequent plans for constructing a new prison at Changi due to uncertainties in the numbers planned for the accommodation (ranging between 650 and 2,500), costs (moving from 2 million Straits dollars to 10 million Straits dollars and back), the area to be used (250 acres to 1,500 acres), and the possibility of the new prison grounds turning into a white elephant.

The tender for erection and completion of the quarters was first awarded to Hup Thye and Co for 16,900 Straits dollars on 26 June 1933,[14] and a 2 September 1933 tender for the prison blocks was reportedly awarded to Chop Woh Hup, a local Chinese construction firm, for 1,278,000 Straits dollars on 8 March 1934.

[17] A subsidiary settlement was developed to support an enterprise of small Chinese traders who would provide necessities to the staff and the prison.

Changi Prison also boasted the use of an advanced and extensive alarm system and had electrical lighting in its cells along with flush-toilets in each.

[20] The death row section of Changi Prison consisted of 24 cells arranged in a horse shoe shaped block around an open air grassy exercise yard.

The building also contained the gallows where judicial hangings were performed, and condemned inmates had a final walk of about 20 meters from their cell to the execution chamber.

[21][22] During World War II, following the Fall of Singapore in February 1942, the Japanese military detained approximately 3,000 civilians in Changi Prison, which was built to house only one-fifth of that number.

These women and also girls sewed quilts for the prison hospital, daringly embroidering their own secret symbols and stories into the squares, including forget-me-nots, butterflies, angels, scenery of trees and sheep, other symbolic flowers and even a domestic sitting room, ships, birds and a map of Scotland, and one of Australia.

They risked severe punishments by sewing, depicting their prison environment and adding dozens, or even over 400 names in one case, onto the cloths.

[26] However, many more prisoners died after being transferred from Changi to various labour camps outside Singapore, including those on the Burma Railway and at Sandakan airfield.

Most of the prisoners of war were eventually repatriated to Japan, but eight former Kempeitai members were found guilty by a military tribunal of torturing 57 internees (which resulted in 15 of them dying) in the "Double tenth" trial on 18 March 1946 at the Supreme Court Building and were sentenced to death.

When Changi Prison was expanded in 2001, the chapel and museum were relocated to a new site 1 kilometre (0.62 mi) away, officially reopening on 15 February 2001.

[38] The inmates were moved in five separate, single day operations between July and August 2009, making it the largest transfer of prisoners in Singapore history.

[39] In 2012, work on building the SPS headquarters on the Complex's grounds began with the $118.5 million contract awarded to Sembawang Engineers and Constructors (SEC).

[40] The building would contain a hydrogen integrated proton-exchange membrane fuel cell power plant to generate clean energy to be supplied to the complex.

[44] Towards the end of 2003, Australian authorities lobbied the Singapore government to preserve the old Changi Prison after knowing that the old Changi Prison would be demolished by April 2004 to redevelop the land for Cluster B,[45][46] on the basis of its historical significance where 15,000 Australians were imprisoned after Singapore fell to imperial Japan in 1942.

[48][49] In 2016, the historical remnants of the old prison – the entrance gate, wall and turrets – was gazetted as the 72nd National Monument of Singapore.