stretched tubular film is then collapsed whilst being heated thereby forming a flat laminated film which is subsequently heat set at a suitable temperature to stabilize the film for example using a matt surfaced roller heat setter e g of the kind described in gb 1124886 a the resultant five layered film consists of two three layered films laminated together by layers of composition c on the interior of the bubble to form a core layer surrounded by two identical layers of composition a and two identical outer layers of composition b which form the two outer surfaces of the film thus the films formed by this method have a b a c a b layered structure the film strictly speaking being a six layer film since the inner core layer formed from composition c is formed by laminating two such layers together in the following examples the outer layer of composition b which forms the outer surface of the film has a mean thickness of from about 0 3 microns u03bcm to about 0 6 microns u03bcm and the central laminated inner layer of composition c has a mean thickness of from about 0 7 microns u03bcm to about 1 2 microns u03bcm the core layer of composition a forms the rest.