There was definitely progress on the ODI front. Beating the World Cup runners-up in a series in their home country is a big achievement. It may be that England just can’t sustain progress in more than one form of the game at a time, though.
One can criticize the scheduling of the test series - not only for the fact that it was during the rainy season, but also the lack of rest between tests. England was obviously tired during the third test, but the test series was apparently decided when Sri Lanka’s batsmen took control in the second innings of the first test.
