During the General Strike of 1926, most employees of his publishing concern were members of National Society of Operative Printers and Assistants (Natsopa). David Coupar Thomson was outraged by the strike and the effect it had on his business. Earlier in 1926, his company took over the rival company John Leng & Co. which produced the "Dundee Advertiser". The strike coincided with the merger. After the strike, Natsopa members were allowed to return provided the members signed a document to say that they had left the union and tender an apology. In March 1952, a strike was caused when a man who had worked for the company since 1921 was discovered to have secretly joined Natsopa in 1939.