Barbecued Fillet & Bread Spiedini

These are very small and easy-to-eat skewers with soft cubes of beef fillet alternating with tiny blocks of bread. Rather like antipasto for adults, and a perfect size for kids. Keeping the meat and bread pieces small is important, as they must be cooked really quickly on all sides so that the bread toasts beautifully rather than burns. I like to make them into about 1 cm (½ inch) cubes but, if