what you need to do is put hot water in the sink, make sure the band is untied and the shitty plastic bit is removed and cut a slot for cap badge. Thenp place said beret in the water. After a few minutes take beret out of water and ring out as much as possible. Place on head and shape, please do not shape to landing pad as you will be laughed at. Keep on head until the shape has "set" then set to one side to dry.
In that case, get some black, quarter-inch knicker elastic, stick a safety-pin through one end and pull it through the leather band. Once you've established how much tension you need on it, sew the two ends neatly together and stuff them back inside the band. Job jobbed.