I think it was mentioned earlier that they have to trade normally up until the announcement, although not exactly ethical.
Many years back I bought a 3 piece suite and they tried over and over to get me to pay cash offering me £100s off but I had a young family and had to put it on my credit card. A week later they went bust, luckily got my money back via credit card being covered. I am sure to this day they knew exactly what they were doing and were told to get cash.... B@st@rds