London Stock Exchange chairman Chris Gibson-Smith decided to add to his stake on the day that the London Stock Exchange's trading facilities were unavailable for more than three hours. He spent just under £100,000 on shares at 769.85p a share. That takes his stake in the London Stock Exchange to 63,757 shares. The market price was soon well below that level as the shares dived on the back of the technical problems and fears about Dubai debt. Dubai World and its subsidiary Nakheel are seeking a debt standstill ahead of a restructuring. Dubai World, which is run by the state, has $59bn of liabilities, its subsidiary Nakheel said in August, but the immediate concern is a $3.5bn bond taken out by Nakheel and maturing on 14 December.Borse Dubai owns 20.6% of the London Stock Exchange. There are worries about what will happen to this stake given the problems in Dubai. This is not the London Stock Exchange's only problem. Competition is getting fiercer. The London Stock Exchange's first half pre-tax profit was hit by increased competition and lower trading volumes. Profit before tax fell to £79.4m in the six month ended 30 September compared with £127m in the previous year on revenue down 9% at £310.9m. Average daily UK equity value traded dropped 16% compared to the second half of the previous year, while the volume of trading in its derivatives markets were 15% better.Broker Merrill Lynch thinks the exchange is likely to lose more market share before new technology developments arrive to halt the decline.Top Director BuysQuintain Estates & Development (QED) Director name: Mr William RuckerAmount purchased: 248,254 @ 80.60p Value: £200,093London Stock Exchange Group (LSE) Director name: Dr Christopher S Gibson-SmithAmount purchased: 12,989 @ 769.85p Value: £99,996Homeserve (HSV) Director name: Mr Barry GibsonAmount purchased: 4,825 @ 1,602.00p Value: £77,296Atkins (WS) (ATK) Director name: Dr Dr Krishnamurthy RajagopalAmount purchased: 10,000 @ 606.00p Value: £60,600Atkins (WS) (ATK) Director name: Mr Keith ClarkeAmount purchased: 10,008 @ 595.85p Value: £59,633CLS Holdings (CLI) Director name: Mr Sten A MortstedtAmount purchased: 12,358 @ 452.84p Value: £55,962NetDimensions (NETD) Director name: Mr Jay ShawAmount purchased: 245,000 @ 15.00p Value: £36,750Barratt Developments (BDEV) Director name: Mr Clive FentonAmount purchased: 26,057 @ 115.13p Value: £29,999GB Group (GBG) Director name: Mr Richard LawAmount purchased: 152,450 @ 19.36p Value: £29,514Barratt Developments (BDEV) Director name: Mr David ThomasAmount purchased: 25,000 @ 114.79p Value: £28,698Top Director SellsJardine Matheson (Singapore) (JAR) Director name: Mr E P K WeatherallAmount sold: 90,000 @ $30.15 Value: $2,713,086Jardine Matheson (Singapore) (JAR) Director name: Mr Adam Phillip Charles KeswickAmount sold: 90,000 @ $30.15 Value: $2,713,086Jardine Matheson (Singapore) (JAR) Director name: Mr Benjamin William KeswickAmount sold: 90,000 @ $30.15 Value: $2,713,086Jardine Matheson (Singapore) (JAR) Director name: Mr Simon L KeswickAmount sold: 90,000 @ $30.15 Value: $2,713,086Big Yellow Group (BYG) Director name: Mr Nicholas VetchAmount sold: 587,195 @ 368.00p Value: £2,160,878Reckitt Benckiser Group (RB.) Director name: Mr Colin R DayAmount sold: 60,000 @ 3,220.00p Value: £1,932,000Big Yellow Group (BYG) Director name: Mr Nicholas VetchAmount sold: 388,000 @ 368.00p Value: £1,427,840Sainsbury (J) (SBRY) Director name: Mr Roger BurnleyAmount sold: 165,000 @ 333.00p Value: £549,450Big Yellow Group (BYG) Director name: Mr James GibsonAmount sold: 124,334 @ 368.00p Value: £457,549Carillion (CLLN) Director name: Mr David HurcombAmount sold: 30,895 @ 300.00p Value: £92,685