text: Petersen was still there at the close on 105, with captain Steven Croft on 34, as the Division One leaders ground out 298-3 from 96 overs in the day.
  Teenager Haseeb Hameed fell 11 short of a second successive Championship ton on 89, while Luke Procter made 45.
  But the unbroken century stand between Petersen and Croft put Lancs on top.
  Having so far put on exactly 100, they will resume on Monday with a third batting bonus point looking a formality - and 14 overs to get a fourth.
  But, if they maintain their current pace of scoring, the Division One leaders will not reach 400 by the time the all-important 110-over mark is reached.
  Hameed followed up his maiden first-class hundred against Warwickshire at Old Trafford last week by taking almost five hours over his 89.
  But it was surpassed by the 41st hundred of 35-year-old South African Test player Petersen's first-class career.
  Lancashire cricket director and head coach Ashley Giles told BBC Radio Manchester:
  "We weren't quite sure what to do when we first turned up this morning. The pitch had a green tinge to it but in the end we decided to toss up and to opt to bat.
  "We knew that pitches at Lord's have been good in recent times so we went with that, and it worked out well for us.
  "Both Alviro Petersen and Haseeb Hameed batted extremely well. We are very lucky to have a number of youngsters who have come into the team and are performing well but we also need our senior players to pull their weight and Alviro did that.
  "We did not expect to be leading the First Division at this stage ,but there is a long way to go."
target: Alviro Petersen made his second County Championship century of the summer to spearhead a solid day's batting by Lancashire against Middlesex at Lord's.