Can a Russian citizen marry an Englishman on a visa class c?

Yes, a Russian citizen can marry an Englishman while on a visa class C, which typically refers to a short-term visit visa. However, they must comply with the legal requirements for marriage in the UK, including giving notice at a local registry office. It's important to note that the visa does not grant the right to stay in the UK beyond its duration, so further visa arrangements would be necessary for residency after marriage.