Extra division. Lords McClusky, Weir and Brand. 5 November 1993. Compulsory powers - purchase - compulsory purchase order - notice to treat - validity - nature and effect - description of land in compulsory purchase order followed in notice to treat - description conforming neither to description of land in proprietor`s title nor to area of land owned by proprietor - whether proprietor entitled to challenge validity of notice to treat where compulsory purchase order unchallenged by lapse of time - Lands Clauses Consolidation (Scotland) Act 1845 (8 & 9 Vict, c19), s17 - Acquisition of Land (Authorisation Procedure)(Scotland) Act 1947 (10 & 11 Geo VI, c42), Sced 1, paras 2 and 15. Personal bar - waiver - whether waiver could operate in such a way as to permit a local authority, acting under its statutory powers, to avoid performance of its statutory duty -whether waiver could validate action, purportedly in pursuance of a statutory power, which was ultra vires.