Ardmore Shipping knew pretty quickly Hafnia's merger proposal was not a good one.

A source close to the situation said the BW Group-backed suitor's 19 June deal — made public on Monday — undervalued Ardmore by more than 18%.

In its press release disclosing the offer, Hafnia said it was offering a 70% premium in an all-stock net asset value to net asset value deal on Ardmore's 12 June closing price of $4.83.