Non-centrosymmetric superconductors (NCS) are believed to be good candidates for unconventional superconductivity. In particular, there is the possibility of Cooper pairs with mixed pairing symmetries. LaPtSi3 forms in the non-centrosymmetric BaNiSn3-type structure, isostructural to the heavy fermion NCS CeRhSi3. It is a type II superconductor (Tc = 1.4 K) with a low upper critical field of around 300 G. We wish to carry out zero, longitudinal and transverse field muon spin relaxation/rotation measurements on a powder sample. We will look for broken time reversal symmetry and measure the temperature dependence of the penetration depth and coherence length. From this we will deduce information about the superconducting gap symmetry. From comparisons with measurements on LaPdSi3, we will examine the effects of increasing the spin-orbit coupling by replacing Pd with heavier Pt atoms.