Amec had tabled an unsuccessful approach worth £690 million last month.
But its shareholders were relieved that the company will not be drawn into a bidding tussle, with the stock climbing 20p or 1.9 per cent to 1,078p.
Kentz headed in the opposite direction, dropping 9.2 per cent or 50.5p to 499p.
The end of the takeover bid came in an otherwise quiet session for the Footsie, which edged up 0.55 points to 6,588.98.
Nicki Dale-Lace, senior sales trader at CMC Markets, said: “Blue-chip stocks have largely held their recent gains as European stocks continue to flirt with the thought of breaking five-year highs.”
Retailers were in focus on a “super-Thursday” for the sector. Half-year results from Morrisons came in just shy of expectations, but the stock rose 2 per cent or 5.3p to 302.5p with traders citing dividend, outlook, and valuation attractions as a trigger for short covering.
Morrisons, the UK’s fourth-biggest supermarket chain, is the tenth most-shorted stock – bets the share price will fall – in the FTSE 100 index, according to data from Markit, while 22 out of 25 analysts covering the stock rating it as either a “hold” or “sell”.
Rival Sainsbury’s was also higher, up 4.7p to 400.8p.
In the FTSE 250, shares in Home Retail Group set the pace after favourable weather drove an 11 per cent jump in like-for-like sales at its Homebase chain.
Shares were lifted 8.8p to 172.7p, while homewares group Dunelm likewise gained ground in the second tier after a well-received set of full-year figures and news of a special dividend windfall to investors.
The group, which saw pre-tax profits leap 12.3 per cent to £108.1 million, rose 10p to 940p.