Slight gains on Wall Street and a smattering of bargain hunters saw the index nudge ahead 9.2 points to 3490.0 by the close of day.
After sprinting out of the starting blocks the Footsie lost all its early lead despite a reassuring statement about the health of the British economy by Downing Street.
Tom Hougaard, trader at spread betting firm City Index, said: “We have to start somewhere and it’s certainty encouraging we have finally managed to close in positive territory.”
Most analysts are likely to remain cautious, however, until the outcome of President George W Bush’s State of the Union address in Washington overnight.
This could provide an insight into the timing of any military action against Iraq as the president responds to yesterday’s UN weapons inspectors’ report.
Uncertainty over Iraq continued to cast a cloud over the City today after it shot forward 57 points in the first quarter of an hour.
In London, defence contractor BAE Systems stormed ahead almost 12%, or 12.5p to 118p.
Oil giants BP and Shell also lent a helping hand with BP up 6p to 362.5p and Shell rose 4p to 353.5p.
But it was another tough day for the British banking sector with Lloyds TSB down 3p at 375p, HSBC off 3.5p at 641p, and Royal Bank of Scotland 11p lower at 1295p.