Update 29th April - I've tried this method out. It is easy, and I've made a video which you can find on today's post.
I hardly ever watch television, except for the Great British Bake-Off, and now I'm following the Great British Sewing Bee - whether the link will let people abroad watch the programmes, I don't know, but in any event BBC iPlayer only keeps the episodes of a series online for about a week after the last instalment, which is next Tuesday.
Last night I settled down to watch the four remaining contestants tackle a set task - a child's dress with a shirred bodice and rouleau straps. I'm not convinced rouleau straps are particularly practical on a child's dress. Because they are cut on the bias they stretch, and a single line of straight stitch will get pulled. Sooner or later the thread will snap. I am totally in agreement with Sandra who disobeyed the rules and made the dress with flat straps.
What I find slightly frustrating about the programme is that it shies away from showing the techniques involved. They didn't show how the contestants did their rouleau straps, there was just passing mention of pulling the tube inside out with a hook. This makes viewers think they will need special equipment if they want to try it at home. They don't.
I've never actually made rouleau straps, but if I ever need to, I will follow these instructions, which show how to make a rouleau and use it for button loops. Ingenious and simple.
Here is the source of the diagrams, a beautiful little book dating from 1928.