The large telescope planned for the Observatorio del Roque de los Muchachos will include an adaptive optics (AO) facility, designed to provide diffraction-limited images in the near infrared. The telescope itself is being designed to allow optimal performance of the AO system. The optical errors of the segmented primary mirror will be specified such that, in closed loop, they do not significantly reduce the Strehl ratio of the final image. In order to achieve high throughput and low emissivity, it is hoped to carry out the adaptive correction by making the telescope secondary mirror adaptive. Turbulence and windspeed profiles measured at La Palma are being used to predict AO performance, as well as to investigate the increase in isoplanatic angle with conjugate height of the deformable mirror, and the focal anisoplanatic errors resulting from the use of laser guide stars.