Having Water Meth on the tanker Valiants (I think it was only in the tanker version) was a godsend. As mentioned by fareastdriver and ian16th it gave a boot up the proverbial at just the right time. I remember an occasion in Malta with number of squadron aircraft recovering to Marham. Each co pilot careufly worked out the T/O and all agreed water meth was not needed on the shortiish runway (now the longest) ln use. The first aircraft rolled clean. However when it was 2/3 down the runway his jet exhaust turned black. Number two made to half way and the rest used it from start. The engineers were not amused as it used up engine life.