Harry Robbins ("H.R.") Haldeman, White House chief of staff. July 30, 1973.

Bob Haldeman was not the stranger to me when he testified that he was to most of the press corps. Known as "Mr. Inside," he was perhaps the most inaccessible of all the President's key advisors. In his own words: "Every president needs an S.O.B., and I'm Nixon's." His testimony before the Committee essentially mirrored Ehrlichman's in content; both men had the same lawyer. Their styles, however, were quite different. He was deferential where Ehrlichman was pugnacious. Haldeman came across as the quintessential advertising executive, talking only about the positive aspects of his "product" and admitting nothing that was negative.
-FJM