The FTSE 100 Index has closed at a record every session since U.K. markets reopened after Christmas — that’s nine trading days — marking a record streak of consecutive all-time highs. Coming on the heels of its best annual performance relative to the Stoxx Europe 600 Index in three decades, the FTSE 100 has climbed 1.9 percent in 2017 as a further slump in sterling boosted its exporters, and commodity producers rallied.