THERE is no doubt Weir Group and Aggreko have been two of Scotland's biggest corporate success stories.

While the UK economy has, until recently, turned in a dire performance amid grim austerity measures put in place by the Coalition Government, engineering group Weir and temporary power specialist Aggreko have enjoyed great success in overseas markets.

And their share prices have surged over the last five-and-a-half years. For a while in late 2008, Weir shares traded below 300p. They closed last night at £26.11. Aggreko shares, for a time in early 2009, traded around 350p . Shares in Aggreko were last night at 1671p.

These two companies' similar ­­share-price graphs are as impressive as they would have been unimaginable in the depths of the global financial and economic crisis in late 2008 and early 2009. Both of these export-orientated companies have surged into the UK's prestigious FTSE-100 index of leading shares. Aggreko has a stock market worth of about £4.3 billion. The market capitalisation of Weir is £5.6bn.

So it would be difficult indeed to overstate the importance of these companies to Scotland.

Both Aggreko and Weir have delivered big news this week.

Glasgow-headquartered Weir has revealed it made an increased bid approach to Finnish engineering company Metso, after having its initial overtures rejected. This increased approach, which valued Metso at about €4.5 billion (£3.7 billion), was also rebuffed.

Metso looks like a decent enough fit for Weir. However, it is difficult to dispel the impression that Weir chief executive Keith Cochrane and his colleagues at the Scottish engineering company might have focused too much on the numbers and not enough on the psychology in their bid approach to Metso.

Back on April 1, when Weir confirmed its initial approach to Metso, the Finnish state came out against such a combination. State-owned investment company Solidium, speaking for its 11% stake in Metso, signalled it was not merely a matter of price, with managing director Kari Jarvinen declaring: "I don't think this is the right time to sell Metso to Weir Group, or to sell it to anyone."

This stance by Solidium always looked pretty adamant, in stark contrast to positions sometimes taken by institutional shareholders in takeover situations which are merely aimed at pushing the price higher.

So it probably didn't really matter that Weir sweetened its all-share acquisition proposal to Metso by 13% from its opening offer.

And, while the Metso deal would probably have been good for Weir and corporate Scotland, the stance of Solidium and presumably other shareholders of the Finnish company has been particularly refreshing. It is nice to see a long-term approach by investors, rather than a knee-jerk reaction to an eye-catching price at a particular point in time.

Weir has, sensibly, given up on Metso for now, rather than racking up the value of its bid proposal to the clearly reluctant Finns still further.

But Mr Cochrane, by going for Metso but not succeeding, has put himself and Weir in the spotlight.

That is the way of things in the mergers and acquisitions arena, although there is no reason to believe Mr Cochrane cannot overcome the challenge he has created for himself.

He has signalled that Weir, while it no doubt still has good organic growth prospects, would benefit from a big acquisition. So all eyes will now be on him to see what he can come up with. And it may well be that Weir's decision to raise its head above the parapet to go for Metso might attract the attention of even bigger players in the sector which might view the Scottish engineering company as an attractive target.

Mr Cochrane will, if he comes up with an alternative major acquisition, need to convince investors such a move is not being made on the rebound from Metso. He will have to persuade them that the target is the right one, and that the price is sensible.

Meanwhile, the best way for Mr Cochrane to avoid Weir becoming prey for someone else is to keep its share price high. The share price will, in no small part, reflect the City's view of how he is doing in running Weir and in seeking out suitable acquisitions.

The strength of Weir's share price in recent years signals the City has been fairly impressed by Mr Cochrane's performance. But we should not underestimate the importance of him continuing to impress after the failure to conclude a takeover of Metso.

While Weir has been in the news on the acquisition front, Aggreko has been hitting the headlines over its change of leadership.

It was announced in February that Rupert Soames, chief executive of Aggreko since 2003 and grandson of wartime leader Winston Churchill, had decided to take up the challenge of heading outsourcing group Serco.

Aggreko confirmed yesterday that senior Centrica executive Chris Weston, who has been responsible for the British Gas operation, would take on the undoubtedly major challenge of following Mr Soames's class act.

Glasgow-based Aggreko also announced that Angus Cockburn, its interim chief executive and long-time chief financial officer, had indicated previously to its board that he had decided not to apply for the top role on a permanent basis and that, after 14 years at the company, he was keen to seek "fresh challenges".

Aggreko is the type of business which could be run from pretty much anywhere but, under the stewardship of Mr Soames and Mr Cockburn, it has been managed from Glasgow.

The company said Mr Weston would be based both in Glasgow and London. The key, from the perspective of corporate Scotland, will be how much time he and his top team actually spend in Glasgow.

Whatever happens from here, both Aggreko and Weir are at their own distinct crossroads.Will Weir prevail as an acquirer, rather than succumbing to a bid itself? And will Glasgow continue to be Aggreko's headquarters in reality, as well as in name?

Only time will tell. But what is for sure is that the paths taken by the top brass of Weir and Aggreko, as they move on from their respective crossroads, will have very major ramifications for corporate Scotland.