Colonial preference occupied an important position in the British tariff of the first half of the nineteenth century. Over fifty classes of goods involved preferential duties, including many of the leading commodities of Britain's import trade and the vast majority of foodstuffs and raw materials on which duties were levied. Colonial preference was also closely associated with the revenue, for, in the late 1830s, seven of the eight principal revenue-earning duties involved varying rates favouring colonial products. For such reasons colonial preference was of crucial importance in the controversy over free trade and it became a major issue in the battle over tariff policy in the post-Napoleonic period. In their opposition to colonial preference free-traders were attacking the general principle of differential duties. Attention, however, was focussed on the duties on only a few commodities, namely timber, sugar and coffee. This concentration arose partly from the fact that these commodities were important items of trade and also because they were in some measure representative of classes of imports and hence served almost as test cases; for example, the sugar and coffee duties involved the issue of preferences for the entire range of West Indian produce and tropical foodstuffs generally, while the timber duties were symbolic of the high duties imposed on many raw materials. More especially the duties on timber, sugar and coffee directly concerned the influential shipowning and West Indian interests who possessed sufficient political power to offer serious resistance to any attempt to modify their favoured position. In the vast literature on Britain's relationship with her colonies in the first half of the nineteenth century much has been written on the changing flow of trade, new attitudes towards the colonies, the breakdown of the old colonial system and colonial preference issues within the free trade struggle. Yet in all these studies little consideration has been given to the subject of customs evasion which led to some strange distortions of normal trading patterns and which occupied a significant place in the dispute over colonial preference in the period.

A general feature of all systems of preferential duties is that compared with a single uniform duty they open up the possibility of customs evasion.