  Here we present a calculation of the temperature-dependent London penetration
depth, $\lambda(T)$, in Ba$_{1-x}$K$_{x}$Fe$_2$As$_2$ (BKFA) on the basis of
the electronic band structure [1,2] and momentum-dependent superconducting gap
[3] extracted from angle-resolved photoemission spectroscopy (ARPES) data. The
results are compared to the direct measurements of $\lambda(T)$ by muon spin
rotation ($\mu$SR) [4]. The value of $\lambda(T=0)$, calculated with \emph{no}
adjustable parameters, equals 270 nm, while the directly measured one is 320
nm; the temperature dependence $\lambda(T)$ is also easily reproduced. Such
agreement between the two completely different approaches allows us to conclude
that ARPES studies of BKFA are bulk-representative. Our review of the available
experimental studies of the superconducting gap in the new iron-based
superconductors in general allows us to state that all hole-doped of them bear
two nearly isotropic gaps with coupling constants $2\Delta/k_{\rm B}T_{\rm
c}=2.5\pm1.5$ and $7\pm2$.
