The FTSE 100 was sharply lower by early afternoon following G20 leaders' warning additional aid will be withheld from the eurozone until its members pledge more support for stricken European countries.
Shares in the Royal Bank of Scotland led the FTSE 100 leader board in early trading despite the group posting a larger than expected loss of £2bn.
The FTSE 100 raced to its highest level in seven months this morning, having made solid gains last week, as mounting optimism over a successful Greek deal lifted sentiment.
European markets are expected to open in the black in early trading, boosted by growing expectations Greece is on the verge of securing a bailout deal.
Shares in the US raced near to highs last seen in 2011, while UK indices reached new highs for 2012, as investors welcomed further talks between Germany and Greece.
Many investors in the current climate would baulk at the words of Laurence Fink, chief executive officer and co-founder of BlackRock, who said investors should have 100% of their investments in equities at the moment.
PSigma's Bill Mott has warned earnings growth forecasts for UK companies are far too high, while equity markets have reached a peak and are set for a correction.
Barclays shares shrugged off a larger than expected fall in profits this morning and a downbeat market to climb over 4% in early trading.
Shares across Asia dropped overnight as the ongoing Greek debacle continued to hit sentiment.