Guest came up against Sir Charles Coghlan, the senior partner of Coghlan and Welsh, in a case before the Court of the Mining Commissioner. Coghlan represented a mining company, which had pegged some gold claims on Guest's client's farm. The Commissioner gave judgment in favour of Guest, who had been instructed to oppose their registration. Following this case, although initially irritated by Guest, Coghlan invited him to join his firm in Salisbury, which Guest did in January 1912. The Salisbury office had been opened by Bernard Tancred. His passing away provided the opportunity for Guest to join the firm as a partner. For a while, the firm was known as Coghlan, Welsh, Townsend and Guest, when Townsend, one of the 1820 Settlers in the Eastern Cape, joined the firm in Salisbury. It reverted to Coghlan, Welsh and Guest, when Townsend died a little time later.