I have to vehemently disagree with the notion that the shabby old shit box at Wellington and Horton should be (have been?) demolished. It is absolutely right that this lot will become a surface parking lot, which decreases the already low pedestrian quality of the intersection, what with the long, dank walk through the underpass and the wide lanes and advanced turns on Wellington. Almost any building there looks better than a hole.
Secondly, it doesn't take a quantum physicist

(sorry, couldn't resist the pun or the image) to figure out what the long-term effect of demolishing buildings downtown is- pretty soon, there is very little of anything to "revitalize". As Jane Jacobs pointed out, old, undistinguished buildings provide great space for nascent ventures because space is cheap - it could be light manufacturing, artist space, upstart internet ventures, whatever. Places from SOHO (NY) to Silicon Valley have thrived because of their initial ability to provide artists and entrepreneurs such space, although "gentrification" has eventually changed those areas significantly. Among other changes, the building stock has gradually been upgraded or replaced, turning former eyesores into fixed-up gems. Demolishing a building eliminates the possibility of such a "grassroots" turn-around and gentrification. Building a new building is almost always more expensive, and the sort of people who build new buildings are apt to charge high rents to "safe" tenants - read: Starbucks and the Gap. When the market doesn't exist for such safe tenants, as it surely doesn't at Wellington and Horton, then, surprise, surprise, the land stays vacant for a long time. Landlords and banks often can't be bothered to upgrade old buildings, however, so, they just knock them down, hoping to hold them for some amazing turnaround (the probability of which they diminish by knocking down neighbourhood buildings), while getting parking revenue in the interim. This kind of behaviour is what has really stopped the heart of neighbourhoods across the US and Canada, and which is evident in such places as Detroit, where vacant lots outnumber abandoned buildings by a ratio of something close to 10 to 1.
So, finally, I would say, the building at the corner was an eyesore. But it was an eyesore with economic and cultural potential, unlike the eyesore parking lot that will replace it.
London needs to stem the tide of such demolitions. I suggest both a carrot and a stick method:
Carrot:
-the City should decrease the economic value of parking lot income with incentives/ subsidization of parking decks, increased street parking, better transit infrastructure
-continue and expand the incentives and grant programs for older downtown buildings (heritage or not)
Stick:
-the City should disallow demolitions unless they are submitted along with a building permit application for the same site, or if the building is deemed by the building inspector to be unsafe and unfixable, in which case a demolition would be allowed, but the resulting vacant lot would be allowed only a temporary parking permit or perhaps not at all
Please tell me what you think.