Another question that faces Cadence's would-be buyers is its rich valuation.

Even at rich valuations and the likelihood that returns in the next 10 years are going to be much less than in the last 10, I still think stocks are a great place for your money.

Among the miners, Antofagasta dropped 2pc after Citigroup cut its rating to "sell", citing a rich valuation relative to the UK sector and slowing volume growth.

The rich valuation underscores the keen interest in acquiring Deutsch, which has been courted for several years by Interpublic and competitors like the Publicis Groupe.

They note that companies like General Electric and Merck are also valued on an earnings-per-share basis, but that those companies get richer valuations because they grow faster.

Greenhill's rich valuation comes after disappointing second-quarter earnings that prompted the stock to fall 14 percent and some of the froth to evaporate.

Citigroup cut its stance to "sell", citing a rich valuation compared with its peers.

You have to be selective because of fairly rich valuations.

"The stocks of the regional banks are still trading at pretty rich valuations compared to the big banks, but if those multiples come down, you'll see an opportunity for some consolidation," Ms. Whitney said.