Michael Spencer, a significant investor in Tungsten Corporation, almost doubled his stake in the cloud-based invoicing business this week. Spencer, who is also the founder of ICAP, paid 253p a share, spending £1.9m in total. His stake in the company now stands at 1.83m shares. The transaction was made as the company posted its half-year interim report for the six months ended October 31st. The group, which was admitted to AIM in mid-October, said trading had been in line with management expectations and its strategy was progressing well. The company, which acquired global business to business e-invoicing network OB10 at the same time it listed, said both the value and volume of invoices had increased as a result of the purchase. Top Director BuysTungsten Corporation (TUNG) Director name: Mr Michael Alan SpencerAmount purchased: 750,000 @ 253.00p Value: £1,897,500Vipera (VIP) Director name: Mr Petter NebyAmount purchased: 8,670,579 @ 5.00p Value: £433,529Vipera (VIP) Director name: Mr Marco CasartelliAmount purchased: 504,110 @ 5.00p Value: £25,206Vipera (VIP) Director name: Mr Martin H W PerrinAmount purchased: 350,000 @ 5.00p Value: £17,500Clarke (T.) (CTO) Director name: Mr David HendersonAmount purchased: 23,000 @ 70.00p Value: £16,100Vipera (VIP) Director name: Mr Marco CasartelliAmount purchased: 319,543 @ 5.00p Value: £15,977Vipera (VIP) Director name: Mr Petter NebyAmount purchased: 319,543 @ 5.00p Value: £15,977Anglo American (AAL) Director name: Mr Phuthuma F. NhlekoAmount purchased: 1,099 @ 1,252.71p Value: £13,767Top Director SellsGooch & Housego (GHH) Director name: Mr Andrew BotelerAmount sold: 134,933 @ 700.00p Value: £944,531Gooch & Housego (GHH) Director name: Mr Terence ScribbinsAmount sold: 122,000 @ 700.00p Value: £854,000St Ives (SIV) Director name: Mr Patrick MartellAmount sold: 385,459 @ 177.64p Value: £684,729St Ives (SIV) Director name: Mr Matthew ArmitageAmount sold: 218,411 @ 177.64p Value: £387,985Jelf Group (JLF) Director name: Mr Phil BartonAmount sold: 199,550 @ 85.70p Value: £171,014Fuller Smith & Turner (FSTA) Director name: Mr M J TurnerAmount sold: 6,772 @ 936.00p Value: £63,386NR