Rule 10 Actions relating to land

may appear and defend, on sending by post to the chief clerk and to each plaintiff and defendant [^f1 at any time before the hearing] a notice claiming that he has an estate or interest in the land to which the action relates or a part thereof;

may, by leave of [^f2 the judge or district judge as the case may be], appear and defend at the hearing, and [ the judge or district judge as the case may be] may, if he thinks fit, add the name of such person as a defendant in the action;