While in custody, he used the name 'Ram Mohammad Singh Azad', which represents the three major religions in India and his anti-colonial sentiment.

[5] In October 1907, while taking his sons by foot to Amritsar, their father collapsed and died at Ram Bagh Hospital.

[8] Shortly thereafter, despite being below the official age of enrolment, Udham Singh persuaded authorities to allow him to serve in the British Indian Army during the First World War.

[8] He was subsequently attached to the lowest ranking labour unit with the 32nd Sikh Pioneers to work on restoration on the field railway from the coast up to Basra.

[8] In 1918, he rejoined the army and was despatched to Basra and then Baghdad, where he carried out carpentry and general maintenance of machinery and vehicles, returning after a year to the orphanage in Amritsar in early 1919.

[8] On 10 April 1919, a number of local leaders allied to the Indian National Congress, including Satyapal and Saifuddin Kitchlew, were arrested under the terms of the Rowlatt Act.

[9] On 13 April, over twenty thousand unarmed people were assembled in Jallianwala Bagh, Amritsar to celebrate the important Sikh festival of Baisakhi, and to peacefully protest the arrests.

[12] In 1924, Singh became involved with the Ghadar Party, organising Indians overseas towards overthrowing colonial rule.

Revolvers, ammunition, and copies of a prohibited Ghadar Party paper called "Ghadr-di-Gunj" ("Voice of Revolt") were confiscated.

[citation needed] Upon his release from prison in 1931, Singh's movements were under constant surveillance by the Punjab Police.

[15] Others wounded in the shooting were Sir Louis Dane; Lawrence Dundas, 2nd Marquess of Zetland;[19] and Charles Cochrane-Baillie, 2nd Baron Lamington.

On 1 April 1940, Singh was formally charged with the murder of Michael O'Dwyer, and remanded in custody at Brixton Prison.

[18] However, political activists who had set up the Shaheed Udham Singh Trust and working with the Indian Workers Association (GB), ran a campaign to have the court record of his statement published along with other material.

[25] This proved successful in 1996, when his speech was published along with three further files covering the trial, and the Ghadar Directory, a document compiled by British intelligence in 1934 detailing 792 people regarded as a threat including Udham Singh.

[25] He started the speech with a denunciation of British Imperialism: At this point he was interrupted by the judge, but after some discussion he continued: At this point, the judge refused to hear any more, but Singh continued: He then thrust his glasses back into his pocket, and exclaimed three words in Hindustani and then shouted: He turned to leave the dock, spitting across the solicitor's table.

[25] When this material was published, it was reported in both British and Asian press, the statement was translated into Gurmukhi script and distributed at the Sikh Vaisaki Festival in Birmingham, April 1997.

[25] John Major, the British prime minister at that time, remarked: "The Amritsar Massacre was an unhappy episode in Indo-British relations which was controversial in both countries.

"[25] In its 18 March 1940 issue, Amrita Bazar Patrika wrote, "O'Dwyer's name is connected with Punjab incidents which India will never forget".

[28] In April 1940, at the Annual Session of the All India Congress Committee held in commemoration of 21st anniversary of the Jallianwala Bagh Massacre, the youth wing of the Indian National Congress Party displayed revolutionary slogans in support of Singh, applauding his action as patriotic and heroic.

The Times of London called him a "fighter for freedom", his actions "an expression of the pent-up fury of the downtrodden Indian people.

[33] In 1999, during the tercentenary of the creation of the Khalsa and the centenary of Singh's birth, he was posthumously awarded the "Nishan-e-Khalsa" by the Anandpur Sahib Foundation.