Six months prior to the invasion, he sent Alby Brook, a B-grade operative, to Vega VI to meet Kalendorf, one of the Knights of Velyshaa, in the hopes of opening up negotiations to form a defence pact against the Daleks. However, Brook was unable to make contact with Kalendorf before the Daleks' arrival.
After Alby made his escape from Vega VI, Tanlee ordered him to travel to the Lopra system and make contact with Espeelius. However, before Alby had left the Vega system, the Aquitania was attacked by the Daleks and he was unable to proceed to the Lopra system. (AUDIO: Invasion of the Daleks)
Following the reconquest of Guria by the Daleks, Alby's scout ship was taken aboard an Earth Alliance battle cruiser, where his travelling companion Gordon Pellan was immediately killed at Tanlee's orders. Tanlee revealed to Alby that Pellan was a highly sophisticated Roboman who was being controlled by the Daleks for the better part of a year. He had spent almost all of this time in the company of Alby. Tanlee believed that, through Pellan, the Daleks were aware of the involvement of the Rhinesberg Corporation, for which Susan Mendes had worked as a geologist prior to the Dalek invasion, in Project Infinity and the existence of Project Infinity itself. (AUDIO: "Death to the Daleks!") However, Alby and Kalendorf later determined that the Daleks learned of it as a result of their raid on the Kar-Charrat library. (AUDIO: Project Infinity) Tanlee then provided Alby with an advanced ship and orders him to find Suz and determine everything that she knows about Project Infinity and, if necessary, kill her. (AUDIO: "Death to the Daleks!")
After many years, the Dalek fleet's siege of the Sol System ended in favour of the Dalek Empire. The President of Earth is left with no option but to surrender to the Daleks, giving them control of the planet. Her final act before communications were lost was to transfer control of all surviving Earth Alliance forces to Tanlee's command. According to the Dalek Supreme, Earth was the final planet in the galaxy which posed a threat to the Daleks. Tanlee's first act was to contact Project Director Espeelius in the Lopra system, ordering him to begin the final phase of Project Infinity.
Tanlee travelled to Carson's Planet, which was occupied by the Daleks before being liberated by the Earth Alliance, where he was reunited with Alby after nine years. He warned Alby that the Daleks had arrived on the planet and were searching for them both. Although Alby was able to make it to a spaceport and escape from Carson's Planet, Tanlee was captured by a Dalek patrol. (AUDIO: "Death to the Daleks!")
Following his capture by the Daleks, Tanlee was converted into a highly sophisticated Roboman in the same manner as Pellan. At the orders of the Dalek Emperor, he travelled to Lopra Minor to supervise the activation of Project Infinity. When Alby, Kalendorf and Mirana arrived on the planet five months later, they realised that Tanlee was now a Dalek agent. Although he intended to have the three of them converted into Robomen, Tanlee was killed when the Daleks from a parallel universe arrived on Lopra Minor and defeated the Enemy Dalek forces on the planet. (AUDIO: Project Infinity)