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Using MEMS technology and transmission electron microscopy we show experimentally multiwalled carbon nan-otubes with a mean fracture strength of larger than 100 GPa, which exceeds the earlier observations by a factor of approximately 3. These results are in excellent agreement with quantum-mechanical estimations. This perfor-mance is made possible by omitting chemical treatments from the sample preparation process, thus avoiding the formation of defects. High-resolution imaging is used to directly determine the number of fractured shells and the chirality of the outer shell. Electron irradiation at 200 keV for 10, 100 and 1800s lead to improvements of the maximum sustainable loads by factors of 2.4, 7.9 and 11.6 compared with non-irradiated samples of similar diameter. This effect is attributed to crosslinking between the shells. This procedure is a cost effective way of customizing the properties of multiwall nanotubes for many applications of interest ranging from nanocomposites to nanodevices.