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You need a bit of specialist equipment but you will end up with a sapphire the size of a large bucket. They are being developed to - among other things - create scratch-proof screens for smart phones.

We also explore the shadowy past of the central bankers' central bank - the Bank of International Settlements. It is an institution that bank-rolled the Nazis yet somehow survived to help design the Euro. So what does the Bank of International Settlements actually do and is it time we got rid of it? We speak to the author of a book on the subject, Adam LeBor.

Plus, how should you greet an acquaintance - a handshake, a hug, a kiss, a curtsey or maybe a salute? Lucy Kellaway has a plan to solve what she calls "hello hell". She is proposing a new international treaty, a Global Greeting Protocol.