By Craig Williams

Copyright bbc

This is a tricky one for John Swinney and his government.

On the one hand, there is a temptation within the SNP to circle the wagons around Hepburn.

He is a popular figure within the group, and there are plenty of members willing to defend him on the basis he was provoked by Ross – who frequently seeks to needle and wind up ministers.

One government source has already contended that sacking everyone who has used the f-word would see nobody left standing.

The trouble is that, by his own admission, Hepburn laid hands on another member while using what he described as “industrious” language.

It may prove difficult to square that with the ministerial code’s requirement to treat colleagues with consideration and respect – particularly when Swinney’s whole pitch as first minister was about uniting parliament and working to build bridges.

There are also likely to be countless opportunities for the Conservatives to bring the issue up, given the parliamentary business minister necessarily has quite a bit to do in the Holyrood chamber.

And Ross is clearly in no mood to let the matter lie. He revealed the incident during First Minister’s Questions – the highest profile moment of the week – and has taken the first opportunity to keep the story rolling with this letter.

Swinney will not want to be dogged with questions about this – he will know he needs to come to a firm and final position swiftly.