Recent experiments have revealed the propagation of a sustained single-head detonation propagation through an obstructed channel. In this study, new experiments and analysis of the complex threedimensional behaviour of such a single-headed wave in stoichiometric hydrogen-oxygen mixtures is presented. An optically accessible channel of square cross-section containing obstacles with 50% area blockage was used in conjunction with soot-foils and dual-axis high-speed schlieren imaging to study the phenomenon over an initial pressure range of 17 kPa to 24 kPa. Detailed analysis of the wave reveals a transverse asymmetry generated by detonation diffraction whereby a transverse detonation propagates in a zig-zag fashion down the channel reflecting off opposite channel sidewalls. Analysis of the single triple-point trajectory reveals a detonation propagation velocity between 1.4 and 0.5V(CJ), with the transverse detonation propagating at a constant 0.9V(CJ) until reflection on the channel sidewall. The trajectory of the triple-point is undisturbed by the presence of obstacles. In the vicinity of the triple-point, flow analysis indicates prompt ignition (<1 mu s induction time) of the gas mixture behind the Mach-stem and transverse waves, confirming the presence of detention waves within the structure. The role of the obstacle in the propagation mechanism is to weaken the Mach-stem detonation through diffraction to generate a separation in the shock and flame, through which the transverse detonation propagates. (C) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.