Having lectured on chemistry and chemical physics at the University of Essex, where, many years ago, around 1975, I heard a lecture on the hydrazine fuel cell by a scientist from the Shell Thornton Research Centre, which was closed down some years ago, I was particularly interested in the article by Richard Lofthouse and the comments by Professor Matthias Holweg. Although energy density is important, so is the environment! I think the hydrazine cell which turns the input into water and nitrogen is good on both counts. Of course, hydrazine is not a pleasant substance but then filling our cars with hydrocarbon fuel we get a dose of benzeene, a noted carcinogen! A Shell research engineer disparaged their effort as they were a hydrocarbon production company: perhaps that is why they did not pursue their development further. Perhaps then we were not as aware of the problems of Global Warming and local pollution. I note that a Japanese motor firm has developed a new catalyst for the hydrazine cell and a car using it. I look forward to driving one!