When Berkshire Hathaway, the investment fund controlled by Warren Buffett, revealed its Q3 2013 transactions in mid-November, it showed that the 'Oracle of Omaha' had been gradually buying up shares of Exxon Mobil (parent company of Esso) during the second and third quarter of this year.

'Gradually buying shares' for Buffett is the equivalent of 'throwing the kitchen sink' to 99.9% of investors…he bought $3.4bn of Exxon shares (around 1% of the company). Even for Buffett that is a bigger than usual purchase (although he did pump $12bn into a joint venture to buy Heinz not long ago).

The investor created headlines, and possibly a mini housing boom, back in February 2012 when he told CNBC that 'I'd buy up a couple hundred thousand single-family homes if I could', such was his belief that US property was an attractive investment at that time. In the following 18 months US house prices increased by 16.5%.

Few would doubt that Buffett knows what he is doing as he is the most successful stock investor of all time with a fortune in excess of $50bn, so does his purchase of Exxon mean that the term 'peak oil' should be back on the economic agenda?

The term began being widely used in 2005 and as oil prices soared towards $150 a barrel in 2008, with many predicting $200 and even $300 barrels of oil in the near future, a global economic crash sent the price of oil back down under $100 a barrel. While many at the time still considered the fall in the oil price a temporary blip, by 2010 people were talking less about peak oil and more about fracking - the process of drilling and injecting fluid into the ground at high pressure in order to fracture shale rocks, which have trapped oil or gas inside.