Sentence:  And with Bolton suffering a wretched run of five straight home defeats - their worst run in 109 years - Chelsea fans would have been forgiven for expecting a comfortable win./ But surely they did not anticipate the ease with which their team raced into an almost <WSD>impregnable</WSD> half-time lead. 
Meaning of the word marked with <WSD> tags:  Too strong to be penetrated.