Alistair Darby, the Chief Executive Officer of Mitchells & Butlers, the UK's largest operator of managed restaurants and pub, has boosted his holding in the group with the purchase of 45,800 shares.Darby, who only took up his current role in October, purchased the shares in two tranches; 44,716 on behalf of his wife Kellie, and the remaining 1,084 for himself. All the shares were bought for 318.45p each. The transaction was made on Tuesday, the same day the group delivered worse-than-expected full-year results and admitted it had made a slow start to the new financial year, partly because of unseasonably warm weather in the same period in 2011. It also warned that further inflationary and regulatory cost pressures would impact the business in the new financial year, and said it was experiencing ongoing alcohol duty increases, further food price inflation and other cost increases, coupled with continued tightness in consumer incomes.Panmure Gordon reiterated its 'sell' rating for the group, saying the outlook in its view was "disappointing" after like-for-like sales fell 0.1% in the first eight weeks of the new financial year. In a statement made on Tuesday, Darby said: "M&B is well positioned to take maximum advantage of our evolving industry and we have the right strategy in place. I look forward to continuing the business transformation to deliver long term earnings growth and shareholder returns." Top Director BuysElektron Technology (EKT) Director name: Mr Keith Anthony DaleyAmount purchased: 1,286,700 @ 16.05p Value: £206,515Mitchells & Butlers (MAB) Director name: Mr Alistair W DarbyAmount purchased: 45,800 @ 318.45p Value: £145,850Thomas Cook Group (TCG) Director name: Ms Harriet GreenAmount purchased: 500,000 @ 23.00p Value: £115,000Grainger (GRI) Director name: Mr Simon Davies Amount purchased: 100,000 @ 112.77p Value: £112,770Energy XXI (Bermuda) (Di) (EXXI) Director name: Mr John Daniel Schiller JrAmount purchased: 2,000 @ $30.95 Value: $61,900Silence Therapeutics (SLN) Director name: Mr Ali MortazaviAmount purchased: 2,400,000 @ 2.50p Value: £60,000F&C Asset Management (FCAM) Director name: Mr Edward BramsonAmount purchased: 54,142 @ 98.89p Value: £53,541BP (BP.) Director name: Prof Dame Ann Dowling Amount purchased: 11,630 @ 429.90p Value: £49,997Silence Therapeutics (SLN) Director name: Mr Jerry RandallAmount purchased: 1,600,000 @ 2.50p Value: £40,000Autoclenz Holdings (ACZ) Director name: Mr James Anthony LeekAmount purchased: 121,000 @ 30.50p Value: £36,905Top Director SellsXstrata (XTA) Director name: Mr Michael DavisAmount sold: 661,590 @ 1,011.73p Value: £6,693,505