Act III begins the next day after lunch with Lady Britomart writing in the library in Wilton Crescent. Sarah is reading in the armchair and Barbara is on the settee ‘in ordinary fashionable dress, pale and brooding’. Lomax enters and notes with a start that Barbara is not wearing her uniform. Sarah then tells him that they are visiting the cannon works this afternoon.
Cusins enters and says how he has had rather a good night. He explains that after the meeting he was drinking, and they all exclaim at this. He tells them he was drinking with Undershaft and then asks Lady Britomart, ‘how could you marry the Prince of Darkness?’
Barbara asks him about the meeting and he says it was simply amazing. 117 conversions took place and they prayed with gratitude for Bodger’s donation and the anonymous one of £5,000 (it is anonymous as Undershaft would not allow them to give his name).
Undershaft appears and the children leave to prepare for their visit. He is left alone with Lady Britomart and she tells him the amount of money their daughters will need, which he agrees to pay. She also wants to talk to him about Stephen, but he says he is not interested in him. Undershaft still wants a foundling to take over the business in keeping with the tradition; however, he has not yet found a fit successor as all the foundlings he can find are exactly like Stephen. When Stephen enters the room, Undershaft says sulkily that he understands he wants to go into the cannon business. He is relieved when Stephen says ‘certainly not’ (as he sees it as trade and, therefore, below him). Stephen intends to devote himself to politics and blames his mother for keeping him in the dark about his father.
His father asks if there is anything he knows or cares about after suggesting the army, navy, church and the bar. Stephen replies that he knows the difference between right and wrong. Undershaft is amused by this and calls him ‘a master of masters’. Stephen controls his temper and says he pretends to know, ‘nothing more than any honorable English gentleman claims as his birthright!’ Undershaft argues that this is everybody’s birthright and that as Stephen knows nothing, this points clearly to him having a political career. Stephen says he will not have the government of his country insulted, and Undershaft reacts with the argument that he and Lazarus are the government of ‘your country’: ‘You will make war when it suits us, and keep peace when it doesn’t.’ Stephen smiles and puts his hand on Undershaft’s shoulder ‘with indulgent patronage’. He tells him that ‘character’ governs England and Undershaft replies that he is a born journalist.
The others enter at this point and Undershaft is asked how he maintains discipline. He explains that the men keep each other in check by snubbing and bullying each other, and ‘the result is a colossal profit, which comes to me.’ Barbara then says she will not forgive him, because when the Salvation Army took his money a man, ‘turned his back to drunkenness and derision’: she sees this as being worse than murder.
In this early part of Act III, Undershaft is derisive of his son’s pretensions and through this it is possible to see yet another attack on England’s aristocracy. Stephen’s political ambitions are also satirized as is the role of government in a democracy. Undershaft undermines the importance and effectiveness of the government when he points out that it is he and Lazarus that pull the political puppet strings. Stephen’s indulgent patronage demonstrates his continuing belief in the character of a gentleman and highlights his naivety and snobbery with regard to working in ‘trade’.