"It seems to us to be obvious that where you obtain an opportunity to work from an offer of employment being made to you, and the offer has been induced by a false representation that you are entitled to work, the false representation continues thereafter for the benefit of the offender who, permitting the representation to continue, is able to retain employment. Once made, it continues to have effect throughout the employment which has been taken up. At any stage had the representation been corrected, it is plain the employment would have ceased."