In 2012, a High Court rejected Assange's final appeal to avoid extradition to Sweden. He faced charges of rape and sexual assault in Sweden pertaining to an incident in 2010. 
The court's ruling in 2012 still applies. Now he is out of the embassy and in British custody, he should promptly be extradited to Sweden and face the serious allegations of sexual misconduct against him. The statute of limitations on the crime has not yet passed. The crime was committed in 2010 and the statute of limitations on rape and sexual assault is ten years in Sweden. While the statute of limitations remains open, a case against Assange can be reopened. Given that the extradition request from Sweden was placed before any request from the US, it should take precedence. Should Sweden file another request, Assange should immediately be extradited.
The charges against Assange were dropped in 2017. Therefore, the original extradition request no longer stands. Assange maintained that the allegations were falsified and were a ruse to get him to Sweden and then extradite him to the United States from there. If there is any inkling that the Swedish authorities would extradite him to the United States, where he would face politically motivated charges and have no access to a fair trial, then the UK cannot extradite him to Sweden in good faith.
[P1] A UK court has already approved an extradition request from Sweden. [P2] Therefore, it should execute this request and extradite him to Sweden.
Rejecting the premises
[Rejecting P1] Those charges were dropped. Therefore, the request no longer stands.