Lightly oil 2 sheets of clingfilm with the oil. Place the 2 chicken breasts, well spaced apart, between the 2 clingfilm sheets and bash with a rolling pin until the chicken is 5 mm (¼ inch) thick.
Heat a griddle or heavy-based frying pan and cook the chicken for 5 minutes, turning once, until golden and cooked through, adding the bacon to the pan for the final 2 minutes.
Spread the tortillas each with 2 tablespoons mayonnaise. Place the chicken breast over the top, then lay 2 bacon rashers on top of the chicken. Sprinkle with the spinach, then roll up tightly, securing with cocktail sticks. Cut in half and serve immediately, or wrap tightly in greaseproof paper and secure with string to transport.