Tomas Lindahl puts together the pieces of base excision repair This was the start of 35 years of successful work, during which Tomas Lindahl has found and examined many of the proteins in the cell’s toolbox for DNA repair. In the beginning of the 1980s, a relationship took him to Great Britain, where he took up a position at the Imperial Cancer Research Fund in London. In 1986, he became director of the newly founded Clare Hall Laboratory, subsequently known for its scientific creativity. Bit by bit, Lindahl pieced together a molecular image of how base excision repair functions, a process in which glycosylases, enzymes similar to the one he had found in 1974, are the first step in the DNA repair process. Base excision repair also occurs in human beings and, in 1996, Tomas Lindahl managed to recreate the human repair process in vitro. The decisive factor for Tomas Lindahl was the realisation that DNA inevitably undergoes change, even when the molecule is located in the cell’s protective environment. However, it had long been known that DNA can be damaged by environmental assaults such as UV radiation. The mechanism used by the majority of cells to repair UV damage, nucleotide excision repair, was mapped by Aziz Sancar, born in Savur, Turkey, and professionally active in the USA.