Ahhhh, I think I have it! The calculation is that Eater is the first Sunday after the first full moon on or after the vernal equinox. So...

If in the Western calandar we have ratified the vernal equinox as Mar 20 or 21 then, as the full moon falls on Mar 22, Easter is very early. If I am right then the Vernal equinox in the Easter calendar must be flagged as a few days later - Meaning it misses the full moon. The next full moon is April 20 so, the Sunday after is the 27th!

Is that right?

Cheers

Dave