It appears that the jqGrid sortname and sortorder properties do not actually cause your data set to be sorted - they just cause the up/down arrows to be displayed.
How can you get your data set to sort on download?
The sort works well when you click the column headers but I want a default sort to be applied to our data.
Update: When we click the next button, the next request sorts the data.
This causes a slightly confusing UI where the data loads with a down arrow on a column - and the data isn't sorted - but when you click next the data is now sorted.
It seems if I omit sortname and sortorder that jqGrid still displays the sort icon - weird.