The very substantial growth in their steamshipping interests during the 1870s had consequences for the family firms within the business group and for the enterprise network to which William Mackinnon provided leadership. Not all were affected equally, or in the same way, but none could avoid the pressures unleashed by the shipping revolution east of Suez or ignore the new commercial opportunities that emerged. Reactions and responses to such forces, however, were also interwoven with other factors. Family demographics meant that those in charge of the older houses in Glasgow, Liverpool and Calcutta were ageing, so that issues of retirement and succession were beginning to play a part in the strategy of these businesses. Conversely youth and energy was to be found among the newer firms started in the late 1860s. Meanwhile, William Mackinnon's gradual translation from the business life of Glasgow to the business life of London meant the replacement of Glasgow and Liverpool by London as a focal point for group operations within Britain. The structure and strategies of the Mackinnon group underwent further evolution as a result of family circumstances (including William's role as head of the ‘clan’), changing market conditions, and developments among the group's external penumbra of allies and associates.

Of the family firms within the group in 1872 (Figure 4.2), the oldest, Mackinnon Frew & Co of Liverpool, fared least well in the post-Suez era. This was partly a matter of bad luck, but mainly the result of the significant transformation taking place in the maritime environment. The upswing in shipping freights of the late 1860s had persuaded Mackinnon Frew & Co to invest in additional tonnage (with help from other family members and their firms), and three new identical iron-hulled sailing ships were added to the firm's small fleet in late 1868 and early 1869, just as the Suez Canal was about to open. The Mackinnon Frew vessels appear to have found plenty of demand for their services during the early years of the decade, although heavy losses at sea cast a gloom over the Liverpool branch of the family. There was nevertheless still sufficient confidence in the future of sailing ships for Mackinnon Mackenzie & Co to put up 25 per cent of the costs of two replacement vessels for Mackinnon Frew & Co in 1875.