"Whenever this sort of thing happens the best people will be getting a lot of inbound calls. This won't be any different," said a senior banker at a rival.
Freeing up the top floors
Jenkins wants his bank to be more balanced and with lower costs to boost profitability.
Cutting thousands of jobs could save the bank more than 1 billion pounds ($1.68 billion) a year based on average pay. Winding down large parts of its trading book will help to reduce the investment bank's use of capital to 30 percent by 2016 from 51 percent last year.
Read MoreBarclays update:Don't expect a 'magic wand'
The result will be a dismantling of much of the bond trading powerhouse built up by Diamond in the decade prior to the 2008/09 financial crisis. Much of the former Lehman business, which includes the U.S. equities and advisory desks, will stay at the heart of the smaller firm.
For Barclays, that means focusing on its strong "home" markets of the United States and Britain, which account for 60 percent of global market business. It will cut back hard in Asia, largely serving only big clients' needs there and Asian customers who want help on overseas deals.
There have already been a series of high profile departures in the United States, including Hugh 'Skip' McGee, the head of its Americas business who was the most senior ex-Lehman banker. The bank also lost Ros Stephenson, Paul Parker and Larry Wieseneck.
"I'm not concerned at all about the level of departures. What we're seeing is a something of a generational shift," Jenkins said on Thursday as he unveiled his plan.
"We're seeing some of the senior leadership saying it's the right time for them to move on," he said. "We're seeing low levels of attrition in the people that are going to be running the bank going forward, the next generation of MDs."
Senior sources at the bank concurred, and said many of the senior people had left after missing out on the top job taken by King, a U.S. native who moved to London for a couple of years in 1999 and stayed for over a decade. He is now based in New York.
Industry sources said this is part of a wider trend in the industry. "I feel that banks are in a mode to reduce the senior level," a source at another bank said. "The only way to protect and promote the mid-level talent is by freeing up the top."
Barclays has said it plans to cut 7,000 investment bank jobs in the next three years, with about 2,000 of those this year.
It plans to put 340 billion pounds of investment bank assets into a new "non-core" unit where they will be run down, so whole teams will be cut. Staff in those areas that the bank wants to keep may have bonuses based on hitting asset reduction targets - something which UBS did as it shrank its business after a bailout by the Swiss state.
Barclays bosses confident despite shareholder disquiet
At Barclays, Eric Bommensath - the former fixed income boss who became co-head of the investment bank with King a year ago - is in charge of the non-core business and no longer sits on the executive committee.
Barclays faces risks in carrying out its plan. It will "meaningfully reduce" the number of clients, with most focus on the top 1,000 who deliver 75 percent of the investment bank's revenues.
The investment bank will also still be left with 490 billion pounds of assets. While smaller than U.S. players such as JP Morgan, it will remain the largest investment bank in Europe with more assets than the "core" businesses of Deutsche Bank and Credit Suisse after they also pruned operations.
Barclays is exiting most commodities business and is likely to retreat from areas including emerging markets and interest rate trading products, structured products, securitization and cross currency swaps.
Areas where the bank is strong - such as rates in the G10 leading economies, foreign exchange and credit trading and debt capital markets - will be less affected. It is also sticking with its equities and advisory operations, which have expanded in the last three years, require less capital and appear set for yet stronger growth.
Bankers said that while Barclays lags some rivals with its plans, it won't be the last to take radical action.
"In the next year or two, more people will shrink or pull out. We've not seen anything meaningful other than UBS and RBS. Deutsche is going through some change and now Barclays, but there's still a lot more to come," a senior rival banker said.
"It's a painful process. The key questions are where do you pick your spots, and you need to be disciplined."