If Slow delays a spell being cast, does finishing the spell require concentration?

@JeremyECrawford If Slow delays a spell being cast, does finishing the spell require concentration? Is the slot lost if it's not finished?

— Armando Doval (@armando_doval) February 28, 2017

If the slow spell delays the casting of a spell, the delayed spell is subject to the rule in "Longer Casting Times" (PH, 202). #DnD https://t.co/naJEhJSwh0

— Jeremy Crawford (@JeremyECrawford) February 28, 2017

@armando_dovalThanks! In that case, does the caster lose their concentration on a previous spell immediately? Yes.

— Jeremy Crawford (@JeremyECrawford) March 1, 2017