Sir – Most of Sir David Madden’s letter Unjustified suffering (January 15) was adequately refuted by Kevin Elliott’s experience, printed above it. I would only like to comment on Sir David’s final comment that thalidomide was tested on animals.

It is true that thalidomide was tested on guinea pigs. Only later (too late) was it realised that in this case the reaction of guinea pigs was not typical of other mammals, including humans.

I believe that this led to legislation that such tests must in future be performed on suitable numbers of at least three unrelated species.

At the time I was working on a pig farm in North Wales and interested in animal physiology, so I made it my business to find out as much as I could about the thalidomide disaster.

Brian Nash, Islip