There will be important details in the notice of refusal you got in 2012. You might consider scanning it and attaching it to your question -- we have members who are skilled in picking out the relevant legal phrasings of those letters.
The visa application explicitly asks you about earlier refusals, so in order not to disclose it, you would need to have outright lied on your application in 2012.
What generally seems to happen in that case is that your 2012 visa application would have been refused under paragraph 320(7A) of the Immigration Rules. This almost comes with an automatic 10-year entry ban under paragraph 320(7B)(d) -- except that the entry ban is not formally triggered until you apply again and the ECO for your new application reviews your 2012 case to figure out whether you "used deception" back then.
Basically you get one chance to convince an ECO that your failure to disclose in 2012 was an excusable mistake -- and if not, you get a formal ban (counting from 2012, but potentially counting from your new application too if they find it to be deceptive in itself).
Usually it is not recommended to try doing that for yourself without qualified legal representation. Perhaps your employer can help procure some legal assistance for you if they want you to come to London badly enough.