) ( A ), THE LEGISLATION OF ONLY ONE MEMBER STATE IS APPLICABLE , THAT THE INSTITUTION OR INSTITUTIONS OF A SINGLE MEMBER STATE , NAMELY THE STATE IN WHOSE TERRITORY THE WORKER IS OR WAS LAST EMPLOYED , MUST BE CONSIDERED COMPETENT FOR THE PURPOSE OF THE APPLICATION OF ARTICLE 18 ( 1 ). THAT CONCLUSION IS MOREOVER CONFIRMED BY ARTICLE 16 OF REGULATION NO 574/72 OF THE COUNCIL OF 21 MARCH 1972 FIXING THE PROCEDURE FOR IMPLEMENTING REGULATION NO 1408/71 ( OFFICIAL JOURNAL , ENGLISH SPECIAL EDITION 1972 ( I ), P . 159 ) REGARDING THE APPLICATION OF THE PROVISIONS OF REGULATION NO 1408/71 RELATING TO SICKNESS , AND MORE PARTICULARLY ARTICLE 18 OF REGULATION NO 1408/71 . BY PROVIDING THAT A CERTIFIED STATEMENT SPECIFYING THE INSURANCE PERIODS COMPLETED PREVIOUSLY UNDER THE LEGISLATION OF OTHER MEMBER STATES MUST BE ISSUED BY THE INSTITUTION OR INSTITUTIONS OF THE MEMBER STATE TO WHOSE LEGISLATION THE WORKER WAS PREVIOUSLY SUBJECT AND MUST BE SUBMITTED TO THE COMPETENT INSTITUTION , THAT PROVISION IS MANIFESTLY BASED ON THE PRINCIPLE WHEREBY THE INSTITUTION OR INSTITUTIONS OF THE MEMBER STATE IN WHOSE TERRITORY THE WORKER IS OR WAS LAST EMPLOYED ARE ALONE COMPETENT TO AGGREGATE INSURANCE PERIODS .
13 THE ANSWER TO THE FIRST THREE QUESTIONS SUBMITTED BY THE SOCIAL SECURITY COMMISSIONER MUST THEREFORE BE THAT ONLY THE COMPETENT INSTITUTION OR INSTITUTIONS OF THE MEMBER STATE IN WHOSE TERRITORY THE WORKER IS OR WAS LAST EMPLOYED ARE COMPETENT TO AGGREGATE THE INSURANCE PERIODS IN ACCORDANCE WITH ARTICLE 18 OF REGULATION NO 1408/71 OF THE COUNCIL OF 14 JUNE 1971 AND THAT ONLY THE LEGISLATION OF THAT MEMBER STATE IS APPLICABLE TO SICKNESS BENEFIT BY VIRTUE OF ARTICLE 13 ( 2 ) ( A ) OF THAT REGULATION .
INVALIDITY BENEFIT
14 THE FOURTH QUESTION SEEKS ESSENTIALLY TO DETERMINE WHETHER A MEMBER STATE MAY , PURSUANT TO ARTICLE 46 ( 3 ) OF REGULATION NO 1408/71 , VALIDLY REDUCE INVALIDITY BENEFIT DUE UNDER ITS LEGISLATION FOLLOWING A PERIOD OF INCAPACITY FOR WORK DURING WHICH THE WORKER WAS GRANTED BENEFIT FOR THAT SAME INCAPACITY , INCLUDING BENEFIT FROM ANOTHER MEMBER STATE , WHICH IS TO BE TAKEN INTO CONSIDERATION IN ACCORDANCE WITH ARTICLE 40 ( 3 ) OF THAT REGULATION .
15 WHEN ASKING THAT QUESTION , THE SOCIAL SECURITY COMMISSIONER HAS IN MIND THE JUDGMENT OF THE COURT OF 21 OCTOBER 1975 IN CASE 24/75 , PETRONI ( 1975 ) ECR 1149 , ACCORDING TO WHICH ARTICLE 46 ( 3 ) OF REGULATION NO 1408/71 IS INCOMPATIBLE WITH ARTICLE 51 OF THE TREATY TO THE EXTENT TO WHICH IT IMPOSES A LIMITATION ON THE OVERLAPPING OF TWO BENEFITS ACQUIRED IN DIFFERENT MEMBER STATES BY A REDUCTION IN THE AMOUNT OF A BENEFIT ACQUIRED UNDER NATIONAL LEGISLATION ALONE .
16 AS IS APPARENT FROM THE DECISION MAKING THE REFERENCE , EVEN IF IT IS ASSUMED THAT THE MEDICAL CONDITIONS PRESCRIBED BY UNITED KINGDOM LEGISLATION ARE SATISFIED , NO ENTITLEMENT TO INVALIDITY BENEFIT WOULD ARISE IN THIS