Marples had a background with a successful road construction company. When opening the M1 motorway, he said: "This motorway starts a new era in road travel. It is in keeping with the bold scientific age in which we live. It is a powerful weapon to add to our transport system." His association with the high-profile construction company Marples Ridgway became a matter of concern to both the public and politicians. As is customary, he resigned as a director of the company in 1951 on becoming a junior minister, but he only sold his shares in the company in 1960 after the company won a contract to build the Hammersmith Flyover, when questions were asked both in the media and also in the Commons on 28 January 1960; he made a statement to the House later that day confirming that the sale of shares was in hand and would be completed "very soon", noting that as part of the agreement he could be required to buy the shares from the purchaser at the original price after he ceased to hold office, if so desired by the purchaser. He sold the shares to his wife. In July 1964, Marples Ridgway and Partners Limited were awarded a £4.1 million contract for the "Hendon Urban Motorway" extension of the M1, in the same year that the company was taken over by the Bath and Portland Group. There was no evidence of any wrongdoing on anyone's part in this or any of the other contracts awarded to the company during his term of office, it did however lead to a sense of unease, not least within the railway sector.