Non-executive directors of companies that both published strong results recently, Petra Diamonds and Marston's, dipped into the market to buy shares on Thursday.Nick Backhouse, an independent director on brewer and pub owner Marston's board, shelled out £37,408 on shares at 149.63p.Marston's is rated a 'buy' by broker Numis and a 'hold' by Jefferies. Recent final results provided further evidence of the company accelerating its transformation to become a predominately managed pub operator, which some analysts expect to support a re-rating of the shares. Over in the small cap mining sector, Gordon Hamilton, a former Deloitte man now a senior non-executive at diamond digger Petra, dug into his pockets for £32,610 to buy shares at 108.70p.Analysts at Canaccord recently reiterated its 'buy' on the company after strong first quarter production numbers. Two large exceptional stones were recovered from the Cullinan mine recently, continuing to indicate that Petra's near-term strategy of managing production from the diluted ore blocks is bearing fruit. The broker said: "Once the mine transitions to production from the undiluted ore from the 2016 financial year at the C-Cut [large project at Cullinan] the proportion of the recovered material from the Western areas of the Kimberlite (known for high frequency of high value gems) should increase substantially. This and further plant improvements are likely to result in an increase in recovery of "special" stones." Top Director BuysHiscox Ltd (HSX) Director name: Mr Bronek E MasojadaAmount purchased: 74,788 @ 149.90p Value: £112,107Hiscox Ltd (HSX) Director name: Mr Bronek E MasojadaAmount purchased: 71,454 @ 149.90p Value: £107,110Marston's (MARS) Director name: Mr Nick Backhouse Amount purchased: 25,000 @ 149.63p Value: £37,408Rurelec (RUR) Director name: Mr Peter Richard Stephen EarlAmount purchased: 250,000 @ 13.25p Value: £33,125Alent (ALNT) Director name: Mr Steve CorbettAmount purchased: 10,000 @ 330.38p Value: £33,038Petra Diamonds Ltd.(DI) (PDL) Director name: Mr Gordon HamiltonAmount purchased: 30,000 @ 108.70p Value: £32,610Eland Oil & Gas (ELA) Director name: Mr George Walter Mitchell MaxwellAmount purchased: 24,203 @ 94.56p Value: £22,886Findel (FDL) Director name: Mr Francois CoumauAmount purchased: 7,648 @ 261.47p Value: £19,997Flowgroup (FLOW) Director name: Mr Tony StiffAmount purchased: 61,885 @ 18.50p Value: £11,449Flowgroup (FLOW) Director name: Mr Tony StiffAmount purchased: 63,959 @ 17.90p Value: £11,449Top Director SellsPlexus Holdings (POS) Director name: Mr Jeffrey (Jeff) ThrallAmount sold: 700,000 @ 245.00p Value: £1,715,000Hiscox Ltd (HSX) Director name: Mr Roberts R S ChildsAmount sold: 146,127 @ 660.49p Value: £965,154Hiscox Ltd (HSX) Director name: Mr Bronek E MasojadaAmount sold: 74,788 @ 681.82p Value: £509,920Hiscox Ltd (HSX) Director name: Mr Bronek E MasojadaAmount sold: 71,454 @ 680.00p Value: £485,887Plexus Holdings (POS) Director name: Mr Bernard van BilderbeekAmount sold: 194,152 @ 245.00p Value: £475,672Hiscox Ltd (HSX) Director name: Mr Roberts R S ChildsAmount sold: 52,017 @ 678.48p Value: £352,925Plexus Holdings (POS) Director name: Mr Graham StevensAmount sold: 116,000 @ 245.00p Value: £284,200Dunelm Group (DNLM) Director name: Mr Nick WhartonAmount sold: 22,685 @ 882.00p Value: £200,082Hiscox Ltd (HSX) Director name: Mr Roberts R S ChildsAmount sold: 15,063 @ 677.20p Value: £102,007OH