The best way to protect yourself is to use limit orders when placing an order to buy or sell a stock or an exchange-traded fund. (See How Your Buy and Sell Orders Get Filled for more.) Look at the bid-ask spread and set your price limit at the bid for selling a stock and at the ask for buying a stock.
Mr Hughes also described the adoption of the working time directive in the UK as a "mistake", telling MPs he supported the government's bid to limit its application.