KENT, England — A quarter-century or so ago, sheep might have been running around these lush green hills at the Gusbourne Estate in southeastern England, but on this fine autumn day a far different scene was unfolding.

A group of fruit pickers roamed around the rows of vines, picking bright clusters of chardonnay grapes. Another group stacked them high in green buckets, where they glimmered gold in the midday sun.

Gusbourne is not an estate in the conventional English sense, but a vineyard that, along with a steadily growing cohort of competitors, is producing some of the finest sparkling wine in the world these days.

And this was not a regular harvest. England’s record hot summer and limited rainfall have provided the perfect conditions for quality fruit and yields, leaving winemakers buzzing over what could potentially be the finest vintage ever for English fizz.