SUMMARY Field and petrographic data relating to the historically important dyke rocks in Shropshire and Staffordshire are reviewed and trace element geochemistry is used to show that separate dyke suites can be differentiated chemically. The dykes have usually suffered late-stage feldspathization, analcitization, mineralization and weathering, making it difficult to characterize them petrographically. The whole-rock geochemistry described in this paper shows that in Shropshire two tholeiitic suites occur, around Acton Reynald and between Clive and Grinshill, while in Staffordshire alkaline basaltic dykes in the northern Butterton–Swynnerton area are chemically different from those in the southern Yarnfield–Norton Bridge area. These latter suites were derived from different magmatic sources. Chemical comparisons with the nearest suitably aligned Tertiary dyke sets in Anglesey and north Lancashire reveal broad, but not precise, comparability with the Shropshire and Staffordshire dykes respectively. It is argued that dyke emplacements were probably vertical rather than lateral and largely took advantage of pre-existing fracture patterns. The discovery of distinct geochemical suites permits reinterpretation of fission track dating relating to dyke emplacement in the late Cretaceous–early Palaeocene phase of the British Tertiary Volcanic Province. The timing of emplacement of the Shropshire dykes accords well with the existence of a north-east-south-west tensional palaeostress field across the British Tertiary Volcanic Province both before and while the effects ( c. 62 Ma) of the Icelandic mantle plume and dome were first apparent and an abortive Gallic sub-plate was developing. Younger K-Ar and fission track dates in Staffordshire (at 52 and 54 Ma respectively) may relate to resetting of the apatite clock by late-stage hydrothermal alteration. A younger, less reliable K-Ar date in Shropshire (50 Ma) may relate to Cu–Pb–Zn–Co–Ni–V mineralization. The north-north-west–south-south-east Staffordshire dykes may relate generally to emplacement in the same stress field, but their alignment may also have been influenced by inherited upper-crustal Malvernoid fractures in the underlying Midlands microcraton. Post-intrusive normal, oblique and wrench faulting, consistent with later Tertiary and Neogene stress fields, affected dykes in Shropshire, but similar effects in Staffordshire are less well documented.