Cavan Medlock is alleged to have arrived at the Duncan Lewis law firm in Harrow, on September 7 last year, armed with a knife and handcuffs, while carrying a Confederate flag and a Nazi flag.
The 29-year-old is accused of threatening a receptionist with the knife before threatening to kill solicitor Toufique Hossain and abusing two other members of staff because of their racial or religious background.
Prosecutors say he is an extreme right-wing terrorist who planned to kill the solicitor because he objected to his involvement in preventing the Government deporting immigrants.
On Wednesday (December 22), Medlock, from Harrow, appeared at the Old Bailey to enter pleas to six charges against him.
He pleaded not guilty to preparation of terrorist acts on or before September 7 last year.
The charge states that he conducted research into the firm of solicitors and Mr Hossain, and equipped himself with a knife, restraints and flags “with a view to kill”.
Medlock denied a separate charge of making a threat to kill the same solicitor.
He pleaded guilty to four other offences relating to the three other staff members.
He admitted battery and threatening the receptionist with a knife and causing racially aggravated alarm, harassment or distress to the two other employees.
During the hearing Mr Justice Wall set a two-week trial for July 11 next year at Kingston Crown Court.
The bearded defendant, who wore black jogging bottoms and a hooded top, was remanded into custody.