an iron fist in a velvet glove

A person who has a gentle, sweet, or unassuming appearance or disposition, but who in reality is particularly severe, forceful, and uncompromising. Tom is in for it now with his wife. She might seem like a nice lady to us, but she's an iron fist in a velvet glove. The new leader of the country rose to power with promises of democracy and equality, but as his despotic intentions came to light he soon proved to be an iron fist in a velvet glove. The patriarch has always been an iron fist in a velvet glove. Everything was smiles and sunshine in his family, unless you made the mistake of ever going against his wishes.

an iron fist in the velvet glove

If you describe someone or something as an iron fist in the velvet glove you mean that they look gentle but in fact they use a lot of force. There is an iron fist in the velvet glove of the charming Irishman as he plots to make Leeds the top team of the new millennium.