AFAIK, standard practice in the Trident was to engage reverse thrust just before touch down using flight idle setting. Where necessary, additional reverse thrust could be initiated by the aircrew during the flare. This usually resulted in a pretty firm touchdown but shortened the unusually long flare (compared to other aircraft) that was often a feature of Trident landings. This effect seemed to get worse on hot days when I would often observe significant reverse thrust being applied when the a/c was still airborne. I wondered if this was connected to the runway temperature enhancing the wing in ground effect phenonenon?