Oil prices are touching all-time highs of over $41 (€34) a barrel, although they have been higher in the past, if allowance is made for inflation.

During the 1979-80 oil crisis after the Iranian revolution - when older motorists will remember queuing at the pumps - oil prices were close to $80 in today's prices. In the earlier 1973 crisis, during the Arab oil embargo, prices were over $42 in today's prices, just a bit above their existing levels.

However, even allowing for inflation, prices are now at their highest level since the 1970s and analysts believe that this could take a toll on economic growth.

The International Monetary Fund estimates that for every $5 a barrel increase, world GDP growth this year could be 0.3 of a percentage point lower.

The lessening world reliance on oil also makes the likely impact slightly weaker than it would have been in the past.

Manufacturing industry - a heavy oil user - has reduced from 30 per cent of world activity in 1970 to 20 per cent today. Oil supplied some 60 per cent of world power in the mid 1970s, falling to around 40 per cent now.

While Western Europe's reliance on Middle-Eastern oil as an energy provider has fallen significantly, the region is still of key strategic importance.

Two-thirds of the world's proven oil reserves lie in Saudi Arabia and four of its neighbours - including Iraq - explaining market nervousness about current developments in the region.