The mode locking of a coupled-cavity KCl:Tl color-centre laser in a Michelson cavity has been compared experimentally with that of the more conventional Fabry-Perot configuration. Either solitonic fibre or low-dispersion, erbium-doped fibre was used in the control cavity. Although both arrangements produced similar pulse durations, the Michelson configuration offered the practical advantage of greater stability. Self-starting mode locking has been observed when the KCl:Tl crystal was located close to the centre of the master cavity, but the ultrashort pulses were accompanied by a cw background or pedestals.