The mystery of the unidentified white cotton has been solved.  it's going to be a bag and is currently going swimmingly.  As ever in life, as one mystery is solved another takes its place. In this instance it appeared that someone has purloined the last few inches of Aunty Biscuits trousers.  She seemed unaware and unconcerned about this.  Further investigation revealed that they are cropped trousers and supposed to have a bit missing.