London Briefing:Even analysts who predicted 2007 would be the year of the takeover have been astonished at the deal frenzy that is gripping stock markets on both sides of the Atlantic.

The first quarter is not yet over but already the merger and acquisition activity has surpassed all expectations.

And the deals just keep getting bigger, as in the Barclays approach to Dutch rival ABN Amro, a move which, if it comes off, will create an £80 billion global banking giant.

As the takeover moves get bigger, so too, do the rumoured deals. The market has been awash with speculation of a £20 billion private equity break-up bid for the Anglo Dutch consumer goods group Unilever, whose household name brands range from Dove and Timotei to Hellman's, Knorr and Ben & Jerry's.

Just a few months ago, talk of a break-up bid for a company as big as Unilever would have been dismissed as fanciful; now it seems perfectly plausible, particularly in the light of Cadbury Schweppes' decision to split itself in two.

The Cadbury demerger plan followed the emergence of activist investor Nelson Peltz as a near 3 per cent shareholder in the sweets to soft drinks group.

Similarly, the Barclays/ABN Amro merger talks follow the recent appearance of the Children's Investment Fund (CIF), a London-based hedge fund, on the Dutch bank's share register.

CIF wants the bank to sell or demerge part of its business and return the proceeds to shareholders. It claims to have the support of a number of ABN Amro's leading shareholders and plans to use the group's annual meeting at the end of April to step up its attack.

Thus Barclays is playing the role of "white knight" for ABN Amro which, although it has underperformed the sector in recent years, has strong positions in Brazil, the US, the Middle East and Asia.

A merger with ABN Amro would be the biggest cross-border financial services deal ever seen in Europe. The enlarged group would hurtle up the global banking league, leapfrogging into fifth position among the world's banks. It would also provide some protection for Barclays, which has repeatedly been rumoured to be in the sights of rivals such as Citigroup or Bank of America.

Barclays already earns more than half its £7.1 billion profit outside its home market and most analysts believe the Dutch bank would be a good fit with the British group's credit card to fund management and investment banking operations.

But many analysts are also sceptical that a deal will be forthcoming.

Although Barclays and the Dutch bank say they are in "exclusive" talks, there are no shortage of other banks keen to ride to ABN's rescue. These would most likely include the Spanish Banco Santander, which owns Abbey National in Britain, and possibly Ulster Bank parent Royal Bank of Scotland, as well as ABN Amro's fellow Netherlands-based bank, ING.

The appearance of a vocal activist investor has heightened the need for ABN Amro to take action, but the group has had many takeover approaches in the past - including several overtures from Barclays - and has always insisted on too high a price.

Both sides will be keen to come up with terms before the agenda for the ABN Amro shareholder meeting is published in the next 10 days. But the trick will be to thrash out a deal that does not leave Barclays open to accusations of over-paying or ABN Amro appearing to have sold out too cheaply.

If their deal fails to achieve this, the Dutch bank will not be the only one in need of a new "white knight".

By 1.15pm today, we'll know whether the speculation that has swept through the Treasury in recent weeks is true: that chancellor Gordon Brown plans to use his 11th and final budget speech to break a 140-year record.

It was back in 1867 that Disraeli romped through his budget speech in just 45 minutes. Coming in under that time would ensure a permanent place in pub quiz trivia-land for Mr Brown.

Such speculation keeps the budget spread-bettors entertained but there are, of course, more weighty matters on the chancellor's mind.

Not least of which will be just how much longer before his marathon stint at the Treasury comes to an end and the long-awaited Brown premiership begins.

Fiona Walsh writes for the Guardian newspaper in London