Derek Mapp, the Non-Executive Chairman of Informa, raised his own personal stake in the company on the same day the publishing and events firm impressed the market with its interim results.Mapp, who has been Chairman since March 2008, on Tuesday bought 80,700 shares from Suffolk Life Annuities Limited at a price of 524.07p each, spending a total of £422,924.Nevertheless, his total holding in the company following the transaction remained unchanged at 100,000 shares, given his interest in Suffolk Life Annuities Limited.Mapp had been on the board of Taylor & Francis Group as a director since 1998 before it merged with Informa in 2004.On Tuesday, the company said that it made a "strong underlying financial performance" in the six months to June 30th and it full-year expectations remain unchanged.Top Director BuysInforma (INF) Director name: Mr Derek MappAmount purchased: 80,700 @ 524.07p Value: £422,924Grainger (GRI) Director name: Baroness Margaret FordAmount purchased: 12,000 @ 171.60p Value: £20,592Bullabulling Gold Limited (DI) (BGL) Director name: Mr Peter John Mansell Amount purchased: 500,000 @ 2.49p Value: £12,450Telecity Group (TCY) Director name: Mr Michael TobinAmount purchased: 2,000 @ 922.84p Value: £18,457Severn Trent (SVT) Director name: Mr Gordon FryettAmount purchased: 1,000 @ 1,762.00p Value: £17,620Alcentra Euorpean Floating Rate Income Fund Ltd Red Ord Shs (AEFS) Director name: Mr Ian FitzgeraldAmount purchased: 15,000 @ 106.95p Value: £16,042Picton Property Income Ltd (PCTN) Director name: Mr Nicholas ThompsonAmount purchased: 22,308 @ 48.00p Value: £10,708Top Director SellsInforma (INF) Director name: Mr Derek MappAmount sold: 80,700 @ 524.00p Value: £422,868BC