The notes run between 12 and 15 years with a weighted average fixed-rate coupon of 2.77%.
Great Portland said the relatively long-dated nature of the notes will significantly extend its average debt maturity and increase available liquidity to more than £500mln.
The group’s loans to value (LTV) figure as at June 30, 2020, was 15%.
In a statement, Martin Leighton, Great Portland’s director of Corporate Finance, said: “We are very pleased with this substantial new debt issue which locks in low cost, long-dated unsecured debt at a time of economic uncertainty and further enhances our significant financial capacity for growth should opportunities emerge.”
Last month, the FTSE 250-listed group said it had received 69% of rent due for the June quarter with support for tenants under pressure from coronavirus being assessed on a case-by-case basis.