Company secretary John Garwood said the value of the group's offices and shops rose 8.4 percent in the first half to 6.28 billion pounds.

"That included a very strong retail investment portfolio performance, which went up by 12.7 percent and for the first time hit the billion pound mark," he said in an interview on Thursday.

"It was a fabulous performance from the retail assets."

The group, which is developing residential property along with more office and retail space, posted underlying profit before tax of 18.9 million pounds for the six months to end-June, up from 10.2 million pounds a year ago.

Its shares were trading up 2.5 percent at 250 pence at 1010 BST.

(Reporting by Paul Sandle; editing by James Davey)