According to the BBC, a scholar, Sheikh Ibrahim Mogra of the Muslim Council of Britain claims that it is a strict rule for a man to obtain the consent

Answer

The Mogra character is a Zindeeq. He speaks bunkum. The consent of the first wife is not at all a requirement for a second marriage. Yes, it is morally proper for the man to inform his wife, and not have a secret 'marriage' with another woman. Zina is a secret affair while Nikah is a public affair.