Why does the edge inscription on the £2 and £1 coins sometimes appear "upside down"?

Sometimes the top of the edge inscription will be pointing towards the obverse of the coin and at other times it will be pointing to the reverse of the coin. There is no right or wrong way. The reason for this is because the edge inscription is rolled onto the coin blank before the blank is struck between two dies to impart the "heads" and "tails". Depending how the blank falls into the coin press determines the way in which the design is struck in relation to the edge inscription. With ordinary circulation coins being struck at over 700 coins per minute it is simply not possible to ensure that each coin is struck with the edge inscription pointing in the same direction.