The paper describes features associated with the ”brittle” cracking mechanism of hydrogen embrittlement in ferritic steel. Such crack advance is characterised by the presence of striations on ”quasi-cleavage” facets running roughly orthogonal to the crack propagation direction. A notch effect is observed, from which is deduced that the cracking is promoted by tensile stress. In iron-3% silicon, observations have been made of both coarse-scale (0.3μm spacing) and fine-scale (30nm spacing) striations.