‘4. The power to award interest on costs prior to judgment is set out inCPR rule 44.2 (g). The rate of such interest is a matter for the court's discretion. As Sharp LJ stated (with the agreement of Patten and Gloster LJJ) in Secretary of State for Energy and Climate Change v Jones[2014] EWCA Civ 363 at [17]: "Ultimately, the court conducts a general appraisal of the position having regard to what is reasonable for both the paying and the receiving parties. This normally involves an assessment of what is reasonable having regard to the class of litigant to which the relevant party belongs, rather than a minute assessment which it would be inconvenient and disproportionate to undertake. In commercial cases the rate of interest is usually set by reference to the short-term cost of unsecured borrowing for the relevant class of litigant, though it is always possible for a party to displace a 'rule of thumb' by adducing evidence, and the rate charged to a recipient who has actually borrowed money may be relevant but is not determinative. See F & C Alternative Investments Ltd v Barthelemy (No. 3) CA [2013] 1 WLR at paragraphs 98, 99 and 102 to 105; Bim Kemi AB v Blackburn Chemicals Ltd[2003] EWCA Civ 889 at 18 and for example, Fiona Trust & Holding Corporation v Privalov[2011] EWHC 664 (Comm) ." Generally, for a party in the UK that paid costs in sterling, the rate applied as representing a commercial rate is the Bank of England base rate plus a percentage determined according to the class of borrower to which the receiving party belongs (e.g. whether it is to be regarded as a "first class" borrower): see Note 44.2.29 to Civil Procedure, Vol. 1 (the White Book). 5. However, where the party conducting the litigation is based overseas and incurred the costs in a foreign currency, the rate relevant to borrowing sterling is not appropriate. Most of the cases involving foreign currency concern the rate of interest on an award of damages, but the applicable principles are the same: Sec of State v Jones at [17]. As the Court of Appeal said in The "Pacific Coloctronis"[1981] 2 Lloyd's Rep 40 at 46, addressing interest on a judgment in US dollars, prima facie the rate of interest applicable should be related to the currency of the judgment. Accordingly, where costs have been incurred in dollars by a litigant operating in the United States, the courts have generally awarded the US Prime Rate as the rate at which the receiving party should reasonably have borrowed: see e.g. Kuwait Airways Corp v Kuwait Insurance Co SAK [2001] 1 Lloyd's Rep IR 678; Mamidoil-Jetoil Greek Petroleum Co SA v Okta Crude Oil Refinery AD[2003] 1 Lloyd's Rep 42 ; Certain Underwriters at Lloyd's London v Syrian Arab Republic[2018] EWHC 385 (Comm) .’