U.K. shares fluctuated on Monday reversing gains recorded earlier after the regional benchmark index FTSE 100 increased to its strongest level in more than 5 ½ years last week. The FTSE 100 decreased by 0.26 point to 6,722.8 as of 11:16 a.m. London time, while the broader FTSE All-Share Index stayed unchanged and Irish ISEQ Index advanced by 1.4%.