Washington's `revolving door' - the movement from government service into the lobbying industry- is regarded as a major concern for policy-making. We study how ex-government staffers benefit from the personal connections acquired during their public service. Lobbyists with experience in the office of a US Senator suffer a 24% drop in generated revenue when that Senator leaves office. The effect is immediate, discontinuous around the exit period and long-lasting. Consistent with the notion that lobbyists sell access to powerful politicians, the drop in revenue is increasing in the seniority of and committee assignments power held by the exiting politician.