Churchill House in St Albans is now fully let.
Modality Systems, a universal communications provider, is to occupy the remaining first floor suite.
They have signed the 7,691 sq ft of office space on a ten year lease.
Other tenants in 28,123 sq ft Grade A office building are Grant Thornton and Spreadex.
Churchill House was recently refurbished by Hale Brown Architects.
Gallagher & Associates and Savills acted for BMO Real Estate Partners.