The chef fought off competition from Steve Love, former executive chef at Loves Birmingham, and Anthony Wright, a senior lecturer at University College Birmingham, at a cook-off at Le Cordon Bleu Cookery School in London on Friday (11 September).
Each finalist had 90 minutes to cook, prepare and present five portions of three different hot garnishes to accompany a fillet of beef.
Speaking after the result Grebenstein told BigHospitality his win had come 'as a bit of a surprise'.
He said: "I wasn't expecting to win to be perfectly honest because it didn't go as well as I thought. There were a few minor mistakes but I'm happy with the outcome. I think [the judges] were looking for someone who can cook even better than they did today, and I'm sure I can do even better than this."
Judging the competition was Bocuse d'Or UK president Brian Turner CBE and former candidates Simon Halstone (2008-2011) and Adam Bennett (2012-2015).
The UK is continuing its bid to host the 2018 European qualifying heat, which Turner said he hoped would build on the country's success of hosting the 2012 Olympics and the first leg of the Tour de France in 2014.
"Recent years have proven how good the UK is at organising these events," he said.
"It's about time we showed the world where we are gastronomically. It's now better than it's ever been, so who knows where it will be in 2018?"
Germany, Denmark, Estonia and The Netherlands are also competing to host the heat.
Grebenstein will now prepare for the European qualifying in Budapest in 2016, where the host of the 2018 event will also be announced.
If successful the chef will go on to compete at the grand final in Lyon in 2017.