Bragg grating inscriptions have been performed within strained, high numerical aperture (NA), germania-doped, monomode fibres. It is shown that the complex dynamics of Bragg grating spectrum formation recorded in these fibres depend strongly on the strain applied to the fibre at the time of photoimprinting. Thermal stability studies of gratings written in strained fibres have been carried out through 30 min isochronal bleaching experiments. It is shown that the stretching of the fibre during the grating fabrication is an important parameter governing the decay of the grating. The implications of these observations are discussed from a practical point of view.