Lepton universality test and the $K^+ \to pi^+ \nu \overline{\nu}$ experiment at the CERN SPS

A measurement of the ratio RK = Γ(K± → e±ν)/Γ(K± → µ±ν), aimed to a test of lepton universality, was performed at CERN by the NA48/2 Experiment during 2003 and 2004. This observable is calculated with very high precision in the framework of the Standard Model (SM), but corrections due to the presence of New Physics could be as high as 3%. The measured value in the 2003-3004 data taking is two times more precise that the world average, but is still insufficient to probe the existence of physics Beyond the SM. The dedicated run for the measurement of RK with sub-percent precision which took data in 2007 is also presented. The P-326 proposal for an experiment to measure the branching ratio of the very rare kaon decay at the CERN SPS is briefly described. The proposed experiment aims to collect events with 10% background in two years data taking period. The status of the project, the R&D; and future prospects for the experiment are discussed.