Duncan joined the International Brigade in February 1937, at the age of 23 years. He was an engineer, member of the TGWU and secretary of Greenford, Communist Party (Ealing, West London)
The Greenford Communist Party had eighteen members and was heavily involved in the Greenford Aid to Spain Committee, established on 13th January 1937. According to T. Duncan the Committee "was more or less inaugurated as a result of our rank & file transport & general workers union bus section", with D. F McCauley as Chair. The women's section of the Communist Party knitted socks for Spain every Thursday afternoon at the Party's headquarters at 51 Rothesay Avenue, Greenford. One speaker at Greenford on Spain was Mr M Bromley who was already in the International Brigade and Michael Finn of the AUBTWU (Bricklayers) reported on a recent trade union delegation to Spain.
The co-coordinator for Southall Aid to Spain was Mrs Grandjean. In February 1937 Southall had three men in Spain, two in the International Brigade and one Ambulance driver. In January 1937 Isabel Brown and
G.Y. Lothian of the TGWU spoke at Southall Communist Party showing of the film made in November 1936 by Ivor Montagu (director) and Norman McLaren (cameraman), entitled "The Defence of Madrid"
Isabel stating, “This fight was not between Fascism and communism but between fascism and democracy”, she also spoke of the urgent need for medical aid, especially warm clothing. This meeting alone raised £70 0s 5d and finished with the singing of the “Internationale”.
The Ealing Spanish Relief Committee Secretary was R.V. Proctor of 24 Bradley Gardens, West Ealing. Jim and Joe Coomes also from Ealing went to Spain to drive ambulances. A.J. Murphy who was living at Beresford Road, Southall wrote to the local paper in July 1936 stating “The Spanish people are defending democracy with their lives they are not doing it for Spain alone, they are doing it for the peoples of all democratic countries in Europe for who can doubt if fascism triumphs in
Spain that tomorrow the Peoples Front in France will be equally attacked.”
He would also have been alarmed at the British Union of Fascists attempt to organise a rally in Southall Park in October 1936. However this was met with a massive counter demonstration under the banner of a campaign organisation, “No fascism in Southall”, the secretaries being D. Romney and J Ross.
Winston Churchill, who had come out for Franco, suggested in the evening Standard 10th August 1936 that “The Spanish government had no legal or moral claim to support since it was being subverted and devalued by Communism” and he continued this support as late as December 1938.