GRAMMAR DETAIL

ことこの上ない

could not be more

Formally emphasizes that the degree of an emotion or evaluation could not be any higher.

Examples

長年の研究が実を結び、喜ばしいことこの上ない。

I could not be happier that the many years of research have borne fruit.

心からありがたいことこの上ない。

I could not be more grateful.

皆様に再会できて、うれしいことこの上ない。

I could not be happier to see all of you again.

Structure: Follow an expression of emotion or quality with ことこの上ない to emphasize formally that its degree could not be greater.
Basic usage: 皆様に再会できて、うれしいことこの上ない。 means being as happy as one could be to see everyone again.

Connecting i-adjectives and na-adjectives
- うれしいことこの上ない retains い before こと. 退屈なことこの上ない inserts な and shows that the construction can also describe an unpleasant quality such as boredom.