The FTSE 100 rose 6.43%, or almost 380 points, in January, making this the strongest start to the year since 1989.
Investors' rotation back into equities helped add £96bn to the value of blue-chip companies over the month.
This is the healthiest month for the FTSE 100 since January 1989, when the index rose by 14.43% (258.7 points).
The index climbed above 6,300 during the first month of 2013, taking it to highs last seen in May 2008, although yesterday's trading was more subdued with the FTSE 100 down 0.73% at 6,276.88.
Strong performance for UK shares in January was matched by global markets with the Dow Jones Industrial Average up 6% over the month, and the Nikkei rising 7.2%.
The FTSE 100 has risen over 18 Januaries since it was launched in 1984. In 1989, the index finished the year 35% higher than its starting position. Meanwhile, annual gains were 14.5% in 1998, when the FTSE 100 had another strong start to the year, up 6.3% in January.
However, fund managers such as Fidelity's Sanjeev Shah have already started to warn of a significant share pullback this year.
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