You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Royal_Institute_of_British_Architects

Context:
RIBA Enterprises is the commercial arm of RIBA, with a registered office in Newcastle upon Tyne, a base at 15 Bonhill Street in London, and an office in Newark. It employs over 250 staff, approximately 180 of whom are based in Newcastle.

Question:
Where does RIBA's business group have its headquarters office?

15 Bonhill Street in London