The KOSB's regimental campaigners challenged the decision in February, issuing a petition claiming that it was "outwith the competency" of a Westminster government to merge or disband a regiment raised in 1689 by act of an independent Scottish parliament.

A preliminary hearing was scheduled for Edinburgh Sheriff Court on Friday 27th May 2005 to determine whether the veterans' case merits further action. This could delay or even overturn the merger of the two historic units and wreck plans for the formation of a new Royal Regiment of Scotland.

The solicitors acting for the campaigners are Alexander Moffat and Co, the Edinburgh firm which also handled the return of the Stone of Destiny to Scotland in 1996. They are regarded as the premier Scottish constitutional legal experts.

A team of lawyers, on behalf of the KOSB's Edinburgh association, re-searched the issues surrounding the regimental case for months before serving a writ on Dr Linda Clarke, QC, advocate-general for Scotland, as Westminster's senior legal representative in Scotland.

The basis of the case is that the KOSB was raised "by beat of drum" near Holyrood Abbey, by emergency order of the Scottish parliament, eight years before the Act of Union created the United Kingdom in 1707, and that Westminster, therefore, has no jurisdiction over the KOSB's fate.

More than 800 volunteers rallied to the standard of the Earl of Leven within two hours on March 18, 1689, to defend Edinburgh and the throne of King William of Orange against a rumoured attack by a Jacobite Highland army loyal to the exiled King James II. The regiment has been in continuous service for 316 years since that event.

If the sheriff court imposes even a temporary ban on the amalgamation, it could seriously disrupt the timetable for the formation of the new Scottish "super-regiment" and could throw the MoD's Future Infantry Structure strategy into disarray.

It would also cast doubt over the disbandment of the Cameronians, Lanarkshire's regiment, in 1968 under defence cutbacks at that time. That regiment, drawn from Covenanters, was also raised by Scottish parliamentary warrant, before the United Kingdom was formed.

The MoD confirmed that the Defence Ministry would be presenting its own legal argument before a sheriff on Friday. "It is a preliminary hearing. There is no point in speculation until we know the outcome."

Donald Fairgrieve, a signatory to the KOSB legal petition and a former officer in the regiment, said: "The act which brought the KOSB into being has never been rescinded. We have done our homework thoroughly." . . . . . read an update on this issue.