One newspaper last week wisely compared law firm mergers to royal weddings - the pre-engagement speculation seems to go on forever and they do not always work out.

Less wisely it mused on the 'mounting excitement' accompanying talks of the impending union of City law firms Theodore Goddard and Richards Butler, 'perhaps inspired' by Prince Edward and Sophie Rhys-Jones's engagement plans.

However, law firm mergers, like relationships - royal or otherwise - are notoriously unpredictable.

The day the story went to press, the talks collapsed.

They were not the first in recent years.Theodore Goddard's managing partner, Peter Kavanagh, says his partners came to a unanimous decision that the 'costs of integration did not outweigh the perceived strength' of their intended match.

According to Ian Guthrie, director of business development at Richards Butler, his firm's partners were 100% behind the merger, and the following day they would have met to say so.

After six months of negotiations - not to mention the huge expense of diverted partner time and due diligence investigations - it was the end of the affair.

Mr Guthrie admitted, with remarkable restraint, that there was a 'mood of disappointment' in the office.Both parties are still on the look-out for alternative mergers.

Denton Hall, which withdrew from the original plans for a tripartite merger last October after a veto fro m its Hong Kong office, is also looking for a merger mate.

And so the clandestine talks in offices continue across the square mile, despite well-documented evidence that finding the right fit is proving elusive.

Indeed, it was second time around for Dentons, as three years ago it broke off talks with what became Cameron McKenna.

Other fruitless merger talks during recent years have included City practice Wilde Sapte and accountants Arthur Anderson, Birmingham law firm Edge & Ellison and Leeds, London and Birmingham firm Pinsent Curtis, and the insurance firms Jacksons in the north east, Weightmans in the north west and City firm Kennedys.The growing number of failed mergers has done little to deter law firms from trying.

In 1996, the merger of Manchester law firms Donns and Philip Conn & Co fell apart after just 28 days.

But Donns are now openly on the look-out for another merger.

A survey of 90 law firms by accountants Smith & Williamson in November 1998, found that 73% of them had been approached with a view to a potential merger in the previous two years, while two-thirds predicted that merger activity would increase in the following 12 months.According to many commentators, apart from the top five City firms, everyone is talking and no-one is off-limits.

Philip Brown of legal consultants Hodgart Temporal and a former managing partner of Wilde Sapte, explains that outside of the so-called magic circle, many medium-sized City practices are 'feeling the squeeze' and finding it increasingly difficult to keep their best lawyers and preserve their best practice areas.

The fee-earning capability of a firm, he argues, may look good at £250,000 per partner, but put these figures next to Allen & Overy's £500,000 per partner and the picture is not so healthy.

Pressure from a few City giants has been compounded by two recent entrants to the market, US law firms and law firms set up in association with the large accountants.In this context, the merger becomes a defensive tactic.

Ronnie Fox, master of the City of London Law Society, as well as senior partner and partnership law expert at City firm Fox Williams, explains: 'Lots of firms feel stronger if they are in larger economic units.

The exposure of a smaller firm is often to do with its reliance on a limited number of clients or sectors.

If you are in a larger firm, typically the larger client will account for a smaller proportion of the total income'.

However, for John Griffith-Jones, adviser to the board at Denton Hall, merger is a necessary step in his firm's attempt to have a world-wide presence.

'We have a strategy to evolve over a period into a global law firm and we won't be able to do that without mergers and combinations with other firms,' he says.

'A London merger, to provide the additional strength we seek particularly in the corporate or banking areas in the London market remains an option which we are looking at very seriously.'While the rationale behind mergers might be easy to grasp, the logistics of meshing two or even three practices together are, as Mr Griffith-Jones readily admits, 'horrendous'.

Mr Fox, who has worked on many law firm mergers, and their 'unhappy consequences' provides a long list of hurdles law firms have to overcome.

These range from practical issues regarding premises and incompatible IT systems, to the more esoteric problems of personality clashes of the partners, and bridging their different financial expectations.

Why should a partner in a richer firm accepts a loss? he asks.

According to Philip Brown, many mergers fail, and 'quite rightl y' so, because they lack a strategic rationale aside from creating a larger, generalist practice.

If you look at the market place, what are they offering the client? he asks.

By contrast mergers in the insurance field - such as the creation of Berrymans Lace Mawer, Beachcroft Wansbroughs and Vizard Staples & Bannister - or health law have worked because they have a rationale: to become a dominant player in a particular market.

The insurance mergers also reflected the trend in the wider insurance market.Such a business case was absent, Mr Brown argues, in the Richards Butler-Theodore Goddard talks.

'I suggest what somebody must have asked is the emperor's clothes question: what does this really give us?' he says.Vanni Treves, senior partner at medium-sized City firm Macfarlanes, says it is a 'great pity' that merger talks cannot be kept secret.

'Failed talks must be demoralising for all parties concerned and I doubt whether it sends the best signals to the outside word,' he observes.Mr Treves is a self-confessed merger sceptic.

He says that his firm has been courted many times but is unlikely to be tempted.

Since the creation of Clifford Chance more than a decade ago, he argues, there has not been a convincing merger.

He also disputes the logic that mergers are a good technique to defend one's position in an increasingly competitive market.

Instead, it can bring new sources of tension in the form of increased overheads and less quality control.

'There's a huge difference between size, and size based on quality and strength of practice.

Size in the abstract won't do the trick.' Contrary to public belief, size is not everything, it would appear.