London:A historic day for one day cricket as the NatWest challenge match between England and Australia at Headingley will be the first to use the new rules in ODIs. For the first time, substitutes will be allowed and there will be 20 overs of fielding restrictions rather than 15. England have already indicated that they will use wicket-keeping batsman Matt Prior as their super-substitute. The first 10 overs will be at the beginning of the innings and then the fielding captain can use two blocks of 5 overs each at his discretion. Australia and England shared the NatWest trophy after a thrilling tie and the three-match one day series before the Ashes looks set to be keenly contested. The new rules will only make it more interesting.