The share price of business and events group Informa slipped on Thursday after the resignation of Finance Director Adam Walker, something which Panmure Gordon believes could ignite bid speculation.The broker maintained its 'buy' rating and 630p target price for the FTSE 250 stock.Analyst Alex DeGroote pointed out that Walker's move - to engineering firm GKN at the end of the year - "follows hot on the heels of news of Peter Rigby's [Chief Executive Officer (CEO)] retirement"."Peter and Adam have worked in tandem for a number of years, and in their absence there is a vacuum of recognisable executive leadership. Informa CEO designate, Stephen Carter, has little Plc experience," he said."In our view, the market should now discount an increased probability of break-up at Informa over the next year or so. Rigby and Walker, to a lesser extent, were the architects of the current group conglomerate structure/strategy. Rational break-up values should yield valuations over 600p, in our view. There is no suggestion that either of these departures is trading-related."The stock was down 1.37% at 503p by mid-morning trade.BC