What the woodwork reveals   Walking with a limp, a lockstephopstep that jolts hip and frame down Main Street I see an unnoticed-until-this-day array of hobbling, rollicking, movement-challenged gimps like me, the Zimmer-pushing halt and lame.   A phenomenon first experienced to this extent when pregnant and, surely, half the eligible population in the Capital and the burbs was enceinte or postpartum with babe in arms or pram.   Like to like. Limp to limp. Baby blimp to blimp.   Bemused, I hobble on.   Robyn Lance   The Three Graces, National Gallery of Scotland   Hobbemas and Rubens hang…