The Civil Procedure (Amendment No. 5) Rules 2014 introduce a new CPR 3.8(4) which allows parties to agree extensions without having to seek the Court’s permission. This rule came into force on 5 June 2014. Prior to 5 June, parties were obliged to pay heed to the prior version of CPR 3.8 which provided that where a rule, practice direction or court order requires a party to do something within a specified time and specifies the consequences  of failure to comply, the parties must seek the court’s permission before extending the deadline. From 5 June, where those conditions apply, the parties may, by written agreement, agree to extend the deadline in question by up to a maximum of 28 days without seeking the court’s permission, provided no hearing date is jeopardised as a result. A similar rule change was brought in earlier this year in respect of clinical negligence cases.

http://www.legislation.gov.uk/uksi/2014/1233/contents/made