Only a handful of companies can or will comply with such a law. It'd take a significant amount of work to backdoor everything and theoretically "secure" said backdoors. Some companies and projects are ideologically opposed to such a thing, oddly enough. It won't work and the UK's GDP won't make it universally appealing. $2.678T is roughly the size of California or a combination of Texas and Florida. Not peanuts, but enough to justify massive amounts of work that won't be directly compensated? Eh, not likely.
Virtually no open source code will allowable in the UK, and virtually no open source projects will comply with the requirements. That alone will do some interesting things to the UK industry, development, etc.