More to come from Great Portland

And there's no sign of this trend abating. New lettings since the end of September are currently running 5.6 per cent ahead of those March ERVs. Furthermore, with office rents in Great Portland's portflolio averaging a modest £44.15 per sq ft, the reversionary potential - which calculates how much more rental income would be realised if all properties were rented at current market rates - comes in at an impressive 21 per cent. Some of this potential is already being crystallised. Two new lettings at £75 per sq ft will fetch almost double the previous passing rent.

Great Portland has also been busy selling completed buildings, which has delivered further gains in a fast-rising market. The Tudor House freehold was sold for a 5 per cent premium to March's book value, while in November contracts were exchanged for the sale of a property in Fetter Lane. The £92.8m sale price was 16 per cent ahead of the March valuation, and Great Portland also receives a £5.1m payment on practical completion of the development. That works out at a return on capital of nearly 83 per cent since the group committed to the scheme.

Chief executive Toby Courtauld remains upbeat about the current cycle - fortunately, as the development pipeline of 2.2m sq ft equates to over half the existing property portfolio. Half of this is on-site or will be completed within the next 18 months, with the remaining half stretching out to 2022.

Analysts at broker Morgan Stanley forecast book value of 671p by March 2015, rising to 744p the year after.