Where a property (usually a flat) is held on a long lease (a lease of more than 21 years as a rule of thumb), the lease terms will generally prohibit the subletting of the flat unless the consent of the freeholder landlord is first obtained. Usually, such consent may not be unreasonably withheld.
An Upper Tribunal decision in 2012, namely, Holding And Management (Solitaire) Ltd v Norton [2012] UKUT 1 (LC), has held charges in that particular case should be £40.00 + VAT for consent fees and no more.
