There are other ways
This isn't unique to TfL, you can look up registration numbers and get vehicle details on other sites too, eBay Motors for example.
Transport for London has provided a handy tool for those who would like to use false numberplates to fool any of the various networks of automatic numberplate recognition (ANPR) cameras now deployed across much of the UK. Using the capital's online congestion charge payment system, anyone can swiftly check what make and colour …
This isn't a TfL innovation. The Government have been publishing details of our vehicles on the web for quite a while now. Go to http://www.vehiclelicence.gov.uk/ and click the "vehicle enquiry" option in the menu.
It will tell you lots of useful stuff, including whether the vehicle is licensed, which is very handy as then you know you won't get pulled in an ANPR tax disc check.
even provides a handy manufacturer / model / colour matching service - just find the ones with the pictures and often enough the plates are there for all to see.
Then use the handy DVLA lookup to check that its got a valid RFL and your sorted.
What could be easier.
IT? - beats all that leg work and you can do it at work