THERE was a better-than-usual turnout for the most recent Referendum Bill committee meeting.

A good number of Holyrood reporters actually bothered to go along to the session, rather than watch it from their offices on the internal TV feed. Some even seemed to be clutching their pencils like French revolutionary knitting needles, as if something gory was about to happen. The reason for the interest was an appearance, around the same table, by some of the big guns from Better Together and Yes Scotland.

We had the two Blairs (pro-UK McDougall and pro-independence Jenkins) sitting side by side, flanked by Denis Canavan, the chairman of the Yes board, and Better Together director Craig Harrow.

In the end not so much as a cross word was said, to the slight disgruntlement of some observers. No needle, so no need for the knitting needles. The session did, however, reveal fears on both sides that their opponents might seek to gain an unfair advantage in the referendum race.

Strict rules, policed by the Electoral Commission watchdog, will kick in as the campaign enters its final stages. In the last 16 weeks, known as the "regulated period", Yes Scotland and Better Together, the political parties and other "permitted participant" campaign groups will have to account for every penny to show they have not exceeded fixed spending limits.

The Scottish and UK governments have also agreed to a "purdah" period in the last 28 days, when ministers will refrain from announcing anything which might be interpreted as a attempt to win votes.

Yes Scotland chairman Mr Canavan told the committee that Westminster should legislate to ensure the UK Government observes purdah. As things stand, the Scottish Government will be bound by its own Referendum Bill but Whitehall has merely given an undertaking as part of the Edinburgh Agreement process. I suspect the committee will back his call, though Yes Scotland is not really too worried about breaches of purdah. The campaign's main fear is that Scotland's 53 pro-UK MPs might be tempted to use their constituency offices to campaign for a No vote. Westminster's rules on using taxpayers' cash for political campaigning are less rigorous and less likely to be enforced than Holyrood's, Yes Scotland insiders claim.

Better Together, meanwhile, suspects the pro-independence campaign of trying to get round its £1.5m spending cap by keeping apparently related groups at arms length. In committee it emerged – to the surprise of many – that Women for Independence and Business for Independence are not officially part of Yes Scotland. That means any cash they spend will not come off Yes Scotland's limit. It's allowed, provided the two groups do not co-ordinate their activities with Yes Scotland. Given the close personal and professional ties between the organisations, there might be questions.

For the record, I'm convinced the two sides are desperate to avoid breaking the rules. Both are keenly aware that "referendum cheat" headlines would be hugely damaging to their cause. It's why they both want greater clarity on the rules from the Electoral Commission and why, of course, they are watching each other so closely.