If, as David Cameron claims, the Conservatives are "the national party of conservation" (Comment, April 23), why does he describe his proposed "green" transport policies in alien metric, instead of our native imperial measurements?      

K W Grimes, Rustington, West Sussex

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Visiting glaciers

Sir - Inspired by David Cameron, we set off last week for Iceland. There, outside Reykjavik on the third day of summer, was the snow line, 50 to 100 metres above sea level - and it snowed some more on each of the next three days we were there.

The glacier we visited had retreated about 40 metres each year for the past 10 years or so, but it is about 30 kilometres long, so at this rate it will take another 750 years to melt.

Our guide told us that, in Viking times, before the Little Ice Age, the Vatna ice cap (the biggest in Iceland) melted so badly that it split into two much smaller ice caps, but today there it is, solid and in one piece and extending over more than 8,000 square kilometres.

He also said that, in Viking times, Iceland grew its own barley, but that now, although it is still being looked at, it appears that the growing season is still too short. As a result, Iceland is still using imported barley for its local spirits.

Cultivation in Iceland is generally carried out on raised beaches created by the land rising some five to 10 metres in the rebound that has taken place since the end of the last Ice Age. This rise is still going on and is out-pacing any possible rise in sea level owing to global warming.

Over to you, David. What did you find out?

David Watt, Hutton, Cumbria