BRUSSELS — Leaders of Europe appeared on Wednesday to be traversing the various stages of grief — anger in particular — as they began to chart a path toward a future without Britain.

In a move heavy with symbolism, Prime Minister David Cameron of Britain returned to London early Wednesday morning after formally informing his fellow leaders in Brussels about the outcome of his country’s referendum last Thursday on leaving the European Union. Cameron has not, however, begun the legal mechanism that would begin the two-year process for withdrawing from the 28-nation bloc, leaving that decision to his successor.

Chancellor Angela Merkel of Germany and President François Hollande of France made clear that Britain could not expect to retain the benefits of EU membership without contributing to the bloc’s budget and accepting its bedrock principle of free movement of workers.

Cameron, before leaving the 27 other EU heads of state to continue their talks without him, told the leaders over a somber dinner that immigration had been a central reason that British voters, by a vote of 52 percent to 48 percent, elected to become the first nation to leave the union.

The bloc faces a bewildering range of concerns beyond the pending divorce with Britain: a continuing migration crisis; pressures on the eurozone; a resurgent Russia; the precarious economy in several countries, notably Greece; terrorist attacks like the one that killed scores at Istanbul’s main airport Thursday night; and populist, anti-European movements roiling domestic politics across many nations.