Mark Devenport BBC Northern Ireland political editor

Divorce can be an ugly business at any time of the year. But it must be especially difficult to be sorting out your matrimonial and financial difficulties on the eve of St Valentine's Day.

So it was that the Ulster Unionist chairman James Cooper arrived at the Orange Order's headquarters in East Belfast on Friday to discuss a row about outstanding fees.

Afterwards both Mr Cooper and the senior Orangemen he met described their discussions as amicable.

Amicable, presumably, in the sense that a divorcing couple can choose to be grown up about things.

Ostensibly the argument is about the failure of some of the Order's 120 delegates to the Ulster Unionist ruling council to pay their annual fees, reckoned to be around �60 per delegate.

The financial row comes against a backdrop of growing disagreement between a party and an order which once spoke with one voice

Ulster Unionist officials reckon the Order should have no representation without taxation, and some suggested that the Order's presence at this march's Annual General Meeting should be cut to as few as 50.

The Orangemen are not the only delegates understood to be in arrears - a similar warning was issued to four constituency associations.

'Rewind a few decades'

To portray this as a dispute over loose change, however, would be to miss the point.

It would be like treating a couple's argument over their joint record collection as being merely a divergence in musical taste.

The financial row comes against a backdrop of growing disagreement between a party and an order which once spoke with one voice.

But when Mr Trimble began steering the Ulster Unionists in a new direction in the wake of the Good Friday Agreement, the joint front crumbled

Rewind a few decades and unionist leaders made no secret of the fact that the two organisations were two sides of the same British coin.

In the 1930s, the then Stormont Prime Minister Lord Craigavon famously boasted: "I am an Orangeman first and a Protestant and a Member of Parliament afterwards."

That umbilical link between the party and the Order remained crucial until recent times.

In 1995, David Trimble owed his elevation from junior MP to party leader to his tough stance over the Order's Drumcree parade.

But when Mr Trimble began steering the Ulster Unionists in a new direction in the wake of the Good Friday Agreement, the joint front crumbled.

'Become alienated'

These days, many in the upper echelons of the Orange Order tend to be more sympathetic to the DUP than to the Ulster Unionists.

The Grandmaster, Robert Saulters, signed Ian Paisley's nomination papers in the run up to last November's assembly election.

The Order's Grand Secretary, Denis Watson, was a DUP candidate.

Some Orangemen believe the dispute over fees is a cover for a purge - 70 fewer Orange delegates would almost certainly be 70 fewer anti-Trimble votes

This month, the DUP held a reception and briefing for senior Orangemen and other representatives of the Loyal Orders at Stormont.

The DUP deputy leader, Peter Robinson, declared his party did not intend to repeat David Trimble's mistakes in allowing itself to become alienated from the wider unionist community.

Against this backdrop, the status of the Orange Order as an affiliated body of the Ulster Unionist Party, and their bloc vote at crucial meetings of the 900-strong ruling council, looks ever more difficult to fathom.

The Ulster Unionist leadership has been talking for years about the need to reform the relationship between the two organisations.

But in the past they have never had the necessary two thirds of the vote to change their rules.

Now an internal Ulster Unionist group has been working on various rule changes.

There are rumours that these could be put to an extraordinary meeting of the council on the eve of the AGM which is set for 27 March.

Some Orangemen believe the dispute over fees is a cover for a purge - 70 fewer Orange delegates would almost certainly be 70 fewer anti-Trimble votes.

But, as with many divorces, there are the children to think about - in this case unionist voters.

The UUP does not want to be seen to expel the Order - it would probably prefer it to jump.

The Order itself may decide that in the long term it should not be tied to any particular party.

If things are not handled delicately the row could end up in the courts - and as divorcees will tell you, if that happens, the only winners are the lawyers.