then-and-there decision

Donald Keen氏訳の人間失格, "No Longer Human" を読んでいます。

I had always imagined that the beaty of virginity was nothing more than the sweet, sentimental illusion of stupid poets, but it really is alive and present in this world. We would get married. In the spring we'd go together on bicycles to see waterfalls framed in geen leaves.
I made up my mind on the spot: it was a then-and-there decision, and I did not hesitate to steal the flower.
Not long afterwards, we were married.

"then-and-there decision" はその前の "made up my mind on the spot" の言い換えの様ですが、辞書で確認します。

・Merriam-Webster: immediately: wanted the money right then and there
・Collins Dictionary: at that precise time and place; at once; on the spot: I started to pack my things right then and there: Also: there and then
・Cambridge English Dictionary: immediately: I suggested he call his mother and he did it there and then.